doc: readd MatrixKind doc

Author: james-d-mitchell

docs/source/data-structures/elements/matrix/matrix.rst

@@ -150,7 +150,40 @@ MatrixKind
 ----------
 
 .. autoclass:: MatrixKind
+    :show-inheritance:
 
+    .. autoattribute:: Boolean
+
+        For matrices over the Boolean semiring.
+
+    .. autoattribute:: Integer
+
+        For matrices over the usual ring of integers.
+
+    .. autoattribute:: MaxPlus
+
+        For matrices over the max-plus semiring.
+
+    .. autoattribute:: MinPlus
+
+        For matrices over the min-plus semiring.
+
+    .. autoattribute:: ProjMaxPlus
+
+        For projective matrices over the max-plus semiring.
+
+    .. autoattribute:: MaxPlusTrunc
+
+        For matrices over the truncated max-plus semiring.
+
+    .. autoattribute:: MinPlusTrunc
+
+        For matrices over the truncated min-plus semiring.
+
+    .. autoattribute:: NTP
+
+        For matrices over the semiring of natural numbers quotiented by `t = t +
+        p`.
 ..
     TODO later summary