code: def __merge_schema_locations(self, ni, incoming_schemaloc):
          
          if ni.schema_location == incoming_schemaloc:  # TODO (bworrell): empty strings?
              return
          elif not ni.schema_location:
              ni.schema_location = incoming_schemaloc or None
          elif not incoming_schemaloc:
              return
          else:
              raise ConflictingSchemaLocationError(ni.uri, ni.schema_location, incoming_schemaloc)
docs: Merge incoming_schemaloc into the given `_NamespaceInfo`, ni.  If we
          don't have one yet and the incoming value is non-None, update ours
          with theirs.  This modifies ni.