code: def delete_reference(self, opaque_ref, global_ref=False):
          
          opaque_ref_value = self._get_reference_value(opaque_ref)
          if global_ref:
              del self.global_refs[opaque_ref_value]
          else:
              del self.local_refs[opaque_ref_value]
docs: Delete the stored mapping of a reference.
  
          :param opaque_ref:       Reference which should be removed.
          :param bool global_ref:  Whether opaque_ref is a local or global
                                   reference.