docs: function (c) {
              if (isString(c)) {
                  var parts = this._splitString(c);
                  var table = parts[0], column = parts[1];
                  if (table) {
                      return new QualifiedIdentifier(table, column);
                  }
                  return column;
  
              } else if (isInstanceOf(c, AliasedExpression)) {
                  return c.expression;
              } else {
                  return c;
              }
          }