docs: fix docstring format

src/dask_awkward/lib/inspect.py

@@ -118,8 +118,9 @@ def report_necessary_buffers(
 def report_necessary_columns(
     *args: Any, traverse: bool = True
 ) -> dict[str, frozenset[str] | None]:
-    r"""Determine the columns necessary to compute a collection built from
-    a columnar source.
+    r"""Get columns necessary to compute a collection
+
+    This function is specific to sources that are columnar (e.g. Parquet).
 
     Parameters
     ----------
@@ -129,25 +130,31 @@ def report_necessary_columns(
     traverse : bool, optional
         If True (default), builtin Python collections are traversed
         looking for any Dask collections they might contain.
+
     Returns
     -------
     dict[str, frozenset[str] | None]
         Mapping that pairs the input layers in the graph to the
         set of necessary IO columns that have been identified by column
         optimisation of the given layer. If the layer is not backed by a
         columnar source, then None is returned instead of a set.
+
     Examples
     --------
     If we have a hypothetical parquet dataset (``ds``) with the fields
+
     - "foo"
     - "bar"
     - "baz"
+
     And the "baz" field has fields
 
     - "x"
     - "y"
+
     The calculation of ``ds.bar + ds.baz.x`` will only require the
     ``bar`` and ``baz.x`` columns from the parquet file.
+
     >>> import dask_awkward as dak
     >>> ds = dak.from_parquet("some-dataset")
     >>> ds.fields