code: function requireModel(filePath, cb) {
          //check if file exist. if not return error
          fs.exists(filePath, function (exists) {
              if (!exists) {
                  soajs.log.error('Requested Model Not Found!');
                  return cb(601);
              }
  
              driver.model = require(filePath);
              return cb();
          });
      }
docs: checks if model file exists, requires it and returns it.
  @param filePath
  @param cb