code: def test_errorhandler_swagger_doc(self, app, client):
      api = restplus.Api(app)
  
      class CustomException(RuntimeError):
          pass
  
      error = api.model("Error", {"message": restplus.fields.String()})
  
      @api.route("/test/", endpoint="test")
      class TestResource(restplus.Resource):
          def get(self):
              """
              Do something
  
              :raises CustomException: In case of something
              """
              pass
  
      @api.errorhandler(CustomException)
      @api.header("Custom-Header", "Some custom header")
      @api.marshal_with(error, code=503)
      def handle_custom_exception(error):
          """Some description"""
          pass
  
      specs = client.get_specs()
  
      assert "Error" in specs["definitions"]
      assert "CustomException" in specs["responses"]
  
      response = specs["responses"]["CustomException"]
      assert response["description"] == "Some description"
      assert response["schema"] == {"$ref": "#/definitions/Error"}
      assert response["headers"] == {
          "Custom-Header": {
              "description": "Some custom header",
              "type": "string",
          }
      }
  
      operation = specs["paths"]["/test/"]["get"]
      assert "responses" in operation
      assert operation["responses"] == {
          "503": {"$ref": "#/responses/CustomException"}
      }
  
imports: from __future__ import unicode_literals
  import json
  import logging
  import pytest
  from flask import Blueprint, abort
  from flask.signals import got_request_exception
  from werkzeug.exceptions import HTTPException, BadRequest, NotFound, Aborter
  from werkzeug.http import quote_etag, unquote_etag
  import flask_restplus
label_desc: Use image node_id 36 for calling the ErrorsTest obj's underlying member method code with example usage: obj.test_errorhandler_swagger_doc(app, client) without return types