code: function inherits(child, parent) {
    if (!child || !parent) return child;
  
    var _arr4 = t.INHERIT_KEYS.optional;
    for (var _i4 = 0; _i4 < _arr4.length; _i4++) {
      var key = _arr4[_i4];
      if (child[key] == null) {
        child[key] = parent[key];
      }
    }
  
    var _arr5 = t.INHERIT_KEYS.force;
    for (var _i5 = 0; _i5 < _arr5.length; _i5++) {
      var key = _arr5[_i5];
      child[key] = parent[key];
    }
  
    t.inheritsComments(child, parent);
  
    return child;
  }
docs: Inherit all contextual properties from `parent` node to `child` node.