code: def rm_back_refs(obj):
      
      for ref in _collect_refs(obj):
          ref['value']._remove_backref(
              ref['field_instance']._backref_field_name,
              obj,
              ref['field_name'],
              strict=False
          )
docs: When removing an object with foreign fields, back-references from
      other objects to the current object should be deleted. This function
      identifies foreign fields of the specified object whose values are not
      None and which specify back-reference keys, then removes back-references
      from linked objects to the specified object.
  
      :param obj: Object for which back-references should be removed