code: function _cloneActiveContext() {
      var child = {};
      child['@base'] = this['@base'];
      child.mappings = _clone(this.mappings);
      child.clone = this.clone;
      child.inverse = null;
      child.getInverse = this.getInverse;
      if('@language' in this) {
        child['@language'] = this['@language'];
      }
      if('@vocab' in this) {
        child['@vocab'] = this['@vocab'];
      }
      return child;
    }
docs: Clones an active context, creating a child active context.
  
  @return a clone (child) of the active context.