code: function (file, enc, cb) {
          var yaml_files = options.src;
  
          if (typeof yaml_files === 'string') {
              yaml_files = [yaml_files];
          }
  
          var yaml_data = {};
  
          // Read all files in order, and override if later files contain same values.
          for (var i = 0; i < yaml_files.length; i++) {
              yaml_data = Object.assign(yaml_data, readYamlFile(yaml_files[i]));
          }
  
          var current_data = file[options.property];
          var new_data = null;
  
          // Merge with possible previous data.
          if (options.override) {
              new_data = Object.assign(current_data, yaml_data);
          } else {
              new_data = Object.assign(yaml_data, current_data);
          }
  
          file[options.property] = new_data;
  
          cb(null, file);
      }
docs: Transform current stream to include a YAML data file.