Fix pos_list api for force atlas

python/cugraph/cugraph/layout/force_atlas2.py

@@ -13,6 +13,7 @@
 
 from cugraph.layout import force_atlas2_wrapper
 from cugraph.utilities import ensure_cugraph_obj_for_nx
+import cudf
 
 
 def force_atlas2(
@@ -55,8 +56,8 @@ def force_atlas2(
         Above 1000 iterations is discouraged.
 
     pos_list: cudf.DataFrame, optional (default=None)
-        Data frame with initial vertex positions containing two columns:
-        'x' and 'y' positions.
+        Data frame with initial vertex positions containing three columns:
+        'vertex', 'x' and 'y' positions.
 
     outbound_attraction_distribution: bool, optional (default=True)
         Distributes attraction along outbound edges.
@@ -131,6 +132,10 @@ def on_train_end(self, positions):
     input_graph, isNx = ensure_cugraph_obj_for_nx(input_graph)
 
     if pos_list is not None:
+        if not isinstance(pos_list, cudf.DataFrame):
+            raise TypeError('pos_list should be a cudf.DataFrame')
+        if set(pos_list.columns) != set(['x', 'y', 'vertex']):
+            raise ValueError('pos_list has wrong column names')
         if input_graph.renumbered is True:
             if input_graph.vertex_column_size() > 1:
                 cols = pos_list.columns[:-2].to_list()