code: function (using, joinType, table, tableAlias) {
              this.__using = using.map(function (u) {
                  return isString(u) ? new Identifier(u) : u;
              });
              this._super(arguments, [joinType, table, tableAlias]);
          }
docs: @lends patio.sql.JoinUsingClause.prototype 
  Represents an SQL JOIN clause with USING conditions.
  Created by {@link patio.Dataset} join methods.
  See {@link patio.sql.JoinClause} for other argument parameters.
  
  @constructs
  @augments patio.sql.JoinClause
  
  @param using the column/s to use when joining.
  @property using <b>READ ONLY</b> the column/s to use when joining.