docs: function mergeOptions() {
    // contruct the call dynamically to handle the variable number of
    // objects to merge
    var args = Array.prototype.slice.call(arguments);
  
    // unshift an empty object into the front of the call as the target
    // of the merge
    args.unshift({});
  
    // customize conflict resolution to match our historical merge behavior
    args.push(customizer);
  
    _merge2['default'].apply(null, args);
  
    // return the mutated result object
    return args[0];
  }