func (q *Query) Start(c Cursor) *Query {
	q = q.clone()
	if c.cc == nil {
		q.err = errors.New("datastore: invalid cursor")
		return q
	}
	q.start = c.cc
	return q
}
func (q *Query) Start(c Cursor) *Query {
	q = q.clone()
	if c.cc == nil {
		q.err = errors.New("datastore: invalid cursor")
		return q
	}
	q.start = c.cc
	return q
}
func ( q * Query ) Start ( c Cursor ) * Query { q = q . clone ( ) if c . cc == nil { q . err = errors . New ( " " ) return q } q . start = c . cc return q }
// Start returns a derivative query with the given start point.
Start returns a derivative query with the given start point .