title: TypeError: Cannot read property 'execute' of undefined in Loopback
body: <p>I created a remote method for cm_comediens using native sql query but when i try to execute it in the explorer i get <code>TypeError 500: Cannot read property 'execute' of undefined</code> </p>
  
  <p>this is the method in my cm_comediens.js file</p>
  
  <pre><code>'use strict';
    var app = require('../../server/server.js');
    var mysql = require('mysql'); 
    module.exports = function(cm_comediens) {
  
      cm_comediens.profile = function (idComedien, cb) {
          var ds = app.dataSource;
          var sql = "SELECT * FROM cm_comediens WHERE id_comedien=?";
  
          ds.connector.execute(sql, idComedien, function (err, cm_comedienss) {
  
              if (err) console.error(err);
  
              cb(err, cm_comedienss);
  
          });
  
      };
  
      cm_comediens.remoteMethod(
          'profile',
          {
              http: { verb: 'get' },
              description: 'Get list of comediens by id',
              accepts: { arg: 'idComedien', type: 'number' },
              returns: { arg: 'data', type: ['cm_comediens'], root: true }
          }
      );
  };
  </code></pre>
  
  <p>table in database and in models in loopback have the same name cm_comediens and the id in the database is : id_comedien and in the model idComedien.
  What's wrong ?</p>