Add docstrings to submesh creation in Python interface

python/dolfinx/mesh.py

@@ -40,6 +40,7 @@
     "locate_entities_boundary",
     "refine",
     "create_mesh",
+    "create_submesh",
     "Mesh",
     "MeshTags",
     "meshtags",
@@ -439,7 +440,18 @@ def create_mesh(
     return Mesh(mesh, domain)
 
 
-def create_submesh(msh, dim, entities):
+def create_submesh(msh: Mesh, dim: int, entities: npt.NDArray[np.int32]):
+    """Create a mesh based on a subset of entities from an existing mesh.
+
+    Args:
+        mesh: Input mesh
+        dim: Topological dimension of the entities to extract
+        entities: Indices of entities in ``msh`` to extract
+    Returns:
+        A quadruplet containing the submesh and three maps from the submesh to
+        the parent mesh. The first map is the entity map, the second map the
+        vertex map (topology), and the third map is the node map (geometry).
+    """
     submsh, entity_map, vertex_map, geom_map = _cpp.mesh.create_submesh(
         msh._cpp_object, dim, entities
     )