def rhs
      raise ScopedSearch::Exception, "Operators with more than 2 children do not have LHS/RHS" if children.length > 2
      children.length == 1 ? children[0] : children[1]
    end
def rhs
      raise ScopedSearch::Exception, "Operators with more than 2 children do not have LHS/RHS" if children.length > 2
      children.length == 1 ? children[0] : children[1]
    end
Return the right-hand side (RHS) operand for this operator.