code: def find_mapping(self, mapped_class):
          
          if not self.__is_initialized:
              self.__is_initialized = True
              self._initialize()
          mapping = None
          for base_cls in mapped_class.__mro__:
              try:
                  mapping = self.__mappings[base_cls]
              except KeyError:
                  continue
              else:
                  break
          return mapping
docs: Returns the mapping registered for the given mapped class or any of
          its base classes. Returns `None` if no mapping can be found.
  
          :param mapped_class: mapped type
          :type mapped_class: type
          :returns: instance of :class:`Mapping` or `None`