code: def _vertex_categorical_dtype(self):
      if self.__vertex_categorical_dtype is None:
          cats = self.vertex_types
          self.__vertex_categorical_dtype = {
              cat: i for i, cat in enumerate(cats)
          }
      return self.__vertex_categorical_dtype
  
imports: import numpy
  import importlib
  from cugraph_service_client.exceptions import CugraphServiceError
  from cugraph_service_client.remote_graph_utils import _transform_to_backend_dtype, _transform_to_backend_dtype_1d, _offsets_to_backend_dtype, MissingModule
label_desc: Use image node_id 13 for calling the RemoteGraph obj's underlying member method code with example usage: obj._vertex_categorical_dtype() and returns: self