Fix hierarchy of the relations page

Author: browniebroke

docs/api-guide/relations.md

@@ -42,7 +42,7 @@ Relational fields are used to represent model relationships.  They can be applie
 
     would solve the issue.
 
-#### Inspecting relationships.
+## Inspecting relationships.
 
 When using the `ModelSerializer` class, serializer fields and relationships will be automatically generated for you. Inspecting these automatically generated fields can be a useful tool for determining how to customize the relationship style.
 
@@ -56,7 +56,7 @@ To do so, open the Django shell, using `python manage.py shell`, then import the
         name = CharField(allow_blank=True, max_length=100, required=False)
         owner = PrimaryKeyRelatedField(queryset=User.objects.all())
 
-# API Reference
+## API Reference
 
 In order to explain the various types of relational fields, we'll use a couple of simple models for our examples.  Our models will be for music albums, and the tracks listed on each album.
 
@@ -77,7 +77,7 @@ In order to explain the various types of relational fields, we'll use a couple o
         def __str__(self):
             return '%d: %s' % (self.order, self.title)
 
-## StringRelatedField
+### StringRelatedField
 
 `StringRelatedField` may be used to represent the target of the relationship using its `__str__` method.
 
@@ -109,7 +109,7 @@ This field is read only.
 
 * `many` - If applied to a to-many relationship, you should set this argument to `True`.
 
-## PrimaryKeyRelatedField
+### PrimaryKeyRelatedField
 
 `PrimaryKeyRelatedField` may be used to represent the target of the relationship using its primary key.
 
@@ -145,7 +145,7 @@ By default this field is read-write, although you can change this behavior using
 * `pk_field` - Set to a field to control serialization/deserialization of the primary key's value. For example, `pk_field=UUIDField(format='hex')` would serialize a UUID primary key into its compact hex representation.
 
 
-## HyperlinkedRelatedField
+### HyperlinkedRelatedField
 
 `HyperlinkedRelatedField` may be used to represent the target of the relationship using a hyperlink.
 
@@ -194,7 +194,7 @@ By default this field is read-write, although you can change this behavior using
 * `lookup_url_kwarg` - The name of the keyword argument defined in the URL conf that corresponds to the lookup field. Defaults to using the same value as `lookup_field`.
 * `format` - If using format suffixes, hyperlinked fields will use the same format suffix for the target unless overridden by using the `format` argument.
 
-## SlugRelatedField
+### SlugRelatedField
 
 `SlugRelatedField` may be used to represent the target of the relationship using a field on the target.
 
@@ -235,7 +235,7 @@ When using `SlugRelatedField` as a read-write field, you will normally want to e
 * `many` - If applied to a to-many relationship, you should set this argument to `True`.
 * `allow_null` - If set to `True`, the field will accept values of `None` or the empty string for nullable relationships. Defaults to `False`.
 
-## HyperlinkedIdentityField
+### HyperlinkedIdentityField
 
 This field can be applied as an identity relationship, such as the `'url'` field on a HyperlinkedModelSerializer.  It can also be used for an attribute on the object.  For example, the following serializer:
 
@@ -265,15 +265,15 @@ This field is always read-only.
 
 ---
 
-# Nested relationships
+## Nested relationships
 
 As opposed to previously discussed _references_ to another entity, the referred entity can instead also be embedded or _nested_
 in the representation of the object that refers to it.
 Such nested relationships can be expressed by using serializers as fields.
 
 If the field is used to represent a to-many relationship, you should add the `many=True` flag to the serializer field.
 
-## Example
+### Example
 
 For example, the following serializer:
 
@@ -311,7 +311,7 @@ Would serialize to a nested representation like this:
         ],
     }
 
-## Writable nested serializers
+### Writable nested serializers
 
 By default nested serializers are read-only. If you want to support write-operations to a nested serializer field you'll need to create `create()` and/or `update()` methods in order to explicitly specify how the child relationships should be saved:
 
@@ -351,7 +351,7 @@ By default nested serializers are read-only. If you want to support write-operat
 
 ---
 
-# Custom relational fields
+## Custom relational fields
 
 In rare cases where none of the existing relational styles fit the representation you need,
 you can implement a completely custom relational field, that describes exactly how the
@@ -363,7 +363,7 @@ If you want to implement a read-write relational field, you must also implement
 
 To provide a dynamic queryset based on the `context`, you can also override `.get_queryset(self)` instead of specifying `.queryset` on the class or when initializing the field.
 
-## Example
+### Example
 
 For example, we could define a relational field to serialize a track to a custom string representation, using its ordering, title, and duration:
 
@@ -396,7 +396,7 @@ This custom field would then serialize to the following representation:
 
 ---
 
-# Custom hyperlinked fields
+## Custom hyperlinked fields
 
 In some cases you may need to customize the behavior of a hyperlinked field, in order to represent URLs that require more than a single lookup field.
 
@@ -417,7 +417,7 @@ The return value of this method should the object that corresponds to the matche
 
 May raise an `ObjectDoesNotExist` exception.
 
-## Example
+### Example
 
 Say we have a URL for a customer object that takes two keyword arguments, like so:
 
@@ -455,9 +455,9 @@ Generally we recommend a flat style for API representations where possible, but
 
 ---
 
-# Further notes
+## Further notes
 
-## The `queryset` argument
+### The `queryset` argument
 
 The `queryset` argument is only ever required for *writable* relationship field, in which case it is used for performing the model instance lookup, that maps from the primitive user input, into a model instance.
 
@@ -467,7 +467,7 @@ This behavior is now replaced with *always* using an explicit `queryset` argumen
 
 Doing so reduces the amount of hidden 'magic' that `ModelSerializer` provides, makes the behavior of the field more clear, and ensures that it is trivial to move between using the `ModelSerializer` shortcut, or using fully explicit `Serializer` classes.
 
-## Customizing the HTML display
+### Customizing the HTML display
 
 The built-in `__str__` method of the model will be used to generate string representations of the objects used to populate the `choices` property. These choices are used to populate select HTML inputs in the browsable API.
 
@@ -477,7 +477,7 @@ To provide customized representations for such inputs, override `display_value()
         def display_value(self, instance):
             return 'Track: %s' % (instance.title)
 
-## Select field cutoffs
+### Select field cutoffs
 
 When rendered in the browsable API relational fields will default to only displaying a maximum of 1000 selectable items. If more items are present then a disabled option with "More than 1000 items…" will be displayed.
 
@@ -498,7 +498,7 @@ In cases where the cutoff is being enforced you may want to instead use a plain
        style={'base_template': 'input.html'}
     )
 
-## Reverse relations
+### Reverse relations
 
 Note that reverse relationships are not automatically included by the `ModelSerializer` and `HyperlinkedModelSerializer` classes.  To include a reverse relationship, you must explicitly add it to the fields list.  For example:
 
@@ -520,7 +520,7 @@ If you have not set a related name for the reverse relationship, you'll need to
 
 See the Django documentation on [reverse relationships][reverse-relationships] for more details.
 
-## Generic relationships
+### Generic relationships
 
 If you want to serialize a generic foreign key, you need to define a custom field, to determine explicitly how you want to serialize the targets of the relationship.
 
@@ -594,7 +594,7 @@ Note that reverse generic keys, expressed using the `GenericRelation` field, can
 
 For more information see [the Django documentation on generic relations][generic-relations].
 
-## ManyToManyFields with a Through Model
+### ManyToManyFields with a Through Model
 
 By default, relational fields that target a ``ManyToManyField`` with a
 ``through`` model specified are set to read-only.
@@ -607,15 +607,15 @@ If you wish to represent [extra fields on a through model][django-intermediary-m
 
 ---
 
-# Third Party Packages
+## Third Party Packages
 
 The following third party packages are also available.
 
-## DRF Nested Routers
+### DRF Nested Routers
 
 The [drf-nested-routers package][drf-nested-routers] provides routers and relationship fields for working with nested resources.
 
-## Rest Framework Generic Relations
+### Rest Framework Generic Relations
 
 The [rest-framework-generic-relations][drf-nested-relations] library provides read/write serialization for generic foreign keys.