code: def _coerce_target(self, target):
          
          if not target or isinstance(target, six.string_types):
              return target
          if not hasattr(target, 'instance'):
              return None
  
          if getattr(target.instance, '_deferred', False):
              model = target.instance._meta.proxy_for_model
          else:
              model = target.instance.__class__
  
          return '%s.%s.%s' % (
              model._meta.app_label,
              model.__name__,
              target.field.name,
          )
docs: Internal method to coerce a target to a string.
  
          The assumption is that if it is not ``None`` and not a string, it is
          a Django ``FieldFile`` object.