code: function processDestination(destination) {
      var destinations = [];
  
      if (_.isArray(destination)) {
        destinations = destination;
      }
      if (_.isString(destination)) {
        destinations.push(destination);
      }
      if (!destinations.length) {
        throw new Error('Destination file not defined.');
      }
      return destinations.map(util.resolveEnsureFile);
    }
docs: Process destination file(s).
  
  @param {string|Array} destination - destination file or an array of
  destination files
  @returns {Array} an array of resolved destination file paths