title: How can output additional headers in flask-restful get handler?
body: <p>I have implemented a flask-restful get handler that returns a number of records in an array. I want to set the header "x-total-count" to the number of records returned. I was able to add a header for every request using @api.representation but I am looking for a way to add the header in my get handler as it is specific to that particular endpoint.</p>
  
  <pre><code>@api.representation('application/json')
  def output_json(data, code, headers=None):
      resp = make_response(json.dumps(data), code)
      headers = dict(headers) if headers else {}
      headers["X-Total-Count"] = str(len(data))
      resp.headers.extend(headers)
      return resp
  
  class Customers(Resource):
      def get(self):
          parser = reqparse.RequestParser()
          parser.add_argument('page', type=int, required=True)
          parser.add_argument('per-page', type=int, required=True)
  
          args = parser.parse_args()
  
          page_num = args['page']
          per_page = args['per-page']
  
          cxn = sqlite3.connect('chinook.db')
          sql = 'SELECT CustomerId, FirstName, LastName, Address, City, PostalCode, State FROM customers ' + \
                'WHERE CustomerId not in (SELECT CustomerId from customers ' + \
                'ORDER BY LastName ASC LIMIT ' + str((page_num-1) * per_page) + ')' + \
                'ORDER BY LastName ASC LIMIT ' + str(per_page)
  
          data = []
          for row in cxn.execute(sql):
              data.append({
                  "id": row[0], "first-name": row[1], "last-name": row[2], "address": row[3],
                  "city": row[4], "state": row[5], "postal-code": row[6] })
  
          cxn.close()
          return data
  </code></pre>