docs: def list_properties(cls):
      """ returns a dictionary of properties assigned to the class"""
      rtn_dict = {}
      for attr in dir(cls):
          if attr not in ["properties", "__doc__", "doc"]:
              attr_val = getattr(cls, attr)
  
              if isinstance(attr_val, MODULE.rdfclass.RdfPropertyMeta):
                  rtn_dict[attr] = attr_val
      return rtn_dict