Add an Explanatory Error Message for uint Types (#4556)

Clarify that unsigned integer types are not supported as vertex ids in the error message.  Resolves issue reported by @ogreen.

Authors:
  - Alex Barghi (https://github.com/alexbarghi-nv)

Approvers:
  - Rick Ratzel (https://github.com/rlratzel)

URL: #4556

python/cugraph/cugraph/structure/graph_implementation/simpleGraph.py

@@ -255,6 +255,13 @@ def __from_edgelist(
             elif elist[source].dtype not in [np.int32, np.int64] or elist[
                 destination
             ].dtype not in [np.int32, np.int64]:
+                if elist[destination].dtype in [np.uint32, np.uint64] or elist[
+                    source
+                ].dtype in [np.uint32, np.uint64]:
+                    raise ValueError(
+                        "Unsigned integers are not supported as vertex ids."
+                        "  Either convert to signed integers or set renumber=True"
+                    )
                 raise ValueError("set renumber to True for non integer columns ids")
 
         # The dataframe will be symmetrized iff the graph is undirected