code: def test_marshal_nested(self):
      model = {
          "foo": fields.Raw,
          "fee": fields.Nested({"fye": fields.String}),
      }
  
      marshal_fields = {
          "foo": "bar",
          "bat": "baz",
          "fee": {"fye": "fum"},
      }
      expected = {
          "foo": "bar",
          "fee": {"fye": "fum"},
      }
  
      output = marshal(marshal_fields, model)
  
      assert output == expected
  
imports: from __future__ import unicode_literals
  import pytest
  from flask_restplus import marshal, marshal_with, marshal_with_field, fields, Api, Resource
label_desc: Use image node_id 20 for calling the MarshallingTest obj's underlying member method code with example usage: obj.test_marshal_nested() without return types