func (s *MergeIterator) Valid() bool {
	if s == nil {
		return false
	}
	if len(s.h) == 0 {
		return false
	}
	return s.h[0].itr.Valid()
}
func (s *MergeIterator) Valid() bool {
	if s == nil {
		return false
	}
	if len(s.h) == 0 {
		return false
	}
	return s.h[0].itr.Valid()
}
func ( s * MergeIterator ) Valid ( ) bool { if s == nil { return false } if len ( s . h ) == 0 { return false } return s . h [ 0 ] . itr . Valid ( ) }
// Valid returns whether the MergeIterator is at a valid element.
Valid returns whether the MergeIterator is at a valid element .