docs: function () {
              var tOpts = this.__opts;
              var clause = (tOpts.having ? "having" : "where"), clauseObj = tOpts[clause];
              if (clauseObj) {
                  var args = argsToArray(arguments);
                  args = args.length === 1 ? args[0] : args;
                  var opts = {};
                  opts[clause] = new BooleanExpression("OR", clauseObj, this._filterExpr(args));
                  return this.mergeOptions(opts);
              } else {
                  throw new QueryError("No existing filter found");
              }
          }