docs: function(key, value)
    {
      if ( key in this.indices )
      {
        this.values[ this.indices[ key ] ] = value;
      }
      else
      {
        this.indices[ key ] = this.values.length;
        AP.push.call( this.values, value );
        AP.push.call( this.keys, key );
      }
  
      return this;
    }