made subcollection into staticmethod

Author: daniel-sanche

packages/google-cloud-firestore/google/cloud/firestore_v1/pipeline_source.py

@@ -172,7 +172,8 @@ def literals(
         """
         return self._create_pipeline(stages.Literals(*documents))
 
-    def subcollection(self, path: str) -> SubPipeline:
+    @staticmethod
+    def subcollection(path: str) -> SubPipeline:
         """
         Initializes a pipeline scoped to a subcollection.
 
@@ -184,7 +185,7 @@ def subcollection(self, path: str) -> SubPipeline:
 
         Example:
             >>> db.pipeline().collection("books").add_fields(
-            ...     db.pipeline().subcollection("reviews")
+            ...     PipelineSource.subcollection("reviews")
             ...         .aggregate(AggregateFunction.average("rating").as_("avg_rating"))
             ...         .to_scalar_expression().as_("average_rating")
             ... )

packages/google-cloud-firestore/tests/unit/v1/test_pipeline_source.py

@@ -17,6 +17,7 @@
 from google.cloud.firestore_v1.async_pipeline import AsyncPipeline
 from google.cloud.firestore_v1.async_query import AsyncQuery
 from google.cloud.firestore_v1.base_document import BaseDocumentReference
+from google.cloud.firestore_v1.base_pipeline import SubPipeline
 from google.cloud.firestore_v1.pipeline import Pipeline
 from google.cloud.firestore_v1.pipeline_source import PipelineSource
 from google.cloud.firestore_v1.query import Query
@@ -121,6 +122,16 @@ def test_literals(self):
         first_stage = ppl.stages[0]
         assert isinstance(first_stage, stages.Literals)
 
+    def test_subcollection(self):
+        expected_path = "/a/b/c"
+        ppl = PipelineSource.subcollection(expected_path)
+        assert isinstance(ppl, SubPipeline)
+        assert len(ppl.stages) == 1
+        first_stage = ppl.stages[0]
+        assert isinstance(first_stage, stages.Subcollection)
+        assert first_stage.path == expected_path
+
+
 
 class TestPipelineSourceWithAsyncClient(TestPipelineSource):
     """