Use public cudf APIs where possible (#578)

cudf's `core` namespace is considered "private", so changing some usages that have public alternative.

Authors:
  - Matthew Roeschke (https://github.com/mroeschke)

Approvers:
  - Ajay Thorve (https://github.com/AjayThorve)

URL: #578

python/cuxfilter/charts/datashader/custom_extensions/graph_assets.py

@@ -81,10 +81,9 @@ def bundle_edges(edges, src="src", dst="dst"):
 
     # Determine each edge's index relative to its bundle
     edges = edges.sort_values(by="bid").reset_index(drop=True)
-    edges["_index"] = (
-        cudf.core.index.RangeIndex(0, len(edges)) - edges["start"]
-    ).astype("int32")
-
+    edges["_index"] = (cudf.RangeIndex(0, len(edges)) - edges["start"]).astype(
+        "int32"
+    )
     # Re-sort the edgelist by edge id and cleanup
     edges = edges.sort_values("eid").reset_index(drop=True)
     edges = edges.rename(columns={"eid": "id"}, copy=False)

python/cuxfilter/charts/datashader/custom_extensions/holoviews_datashader.py

@@ -229,7 +229,7 @@ def __init__(self, **params):
     def _compute_clims(self):
         if not isinstance(
             self.source_df[self.aggregate_col].dtype,
-            cudf.core.dtypes.CategoricalDtype,
+            cudf.CategoricalDtype,
         ):
             self.clims = get_min_max(self.source_df, self.aggregate_col)
 
@@ -238,7 +238,7 @@ def _compute_datashader_assets(self):
         self.cmap = {"cmap": self.color_palette}
         if isinstance(
             self.source_df[self.aggregate_col].dtype,
-            cudf.core.dtypes.CategoricalDtype,
+            cudf.CategoricalDtype,
         ):
             self.cmap = {
                 "color_key": {