func (lt Lt) IsValid() bool {
	return len(lt) > 0
}
IsValid tests if this Eq is valid
package builder
import "fmt"
func WriteMap(w Writer, data map[string]interface{}, op string) error {
	var args = make([]interface{}, 0, len(data))
	var i = 0
	for k, v := range data {
		switch v.(type) {
		case expr:
			if _, err := fmt.Fprintf(w, "%s%s(", k, op); err != nil {
				return err
			}
			if err := v.(expr).WriteTo(w); err != nil {
				return err
			}
			if _, err := fmt.Fprintf(w, ")"); err != nil {
				return err
			}
		case *Builder:
			if _, err := fmt.Fprintf(w, "%s%s(", k, op); err != nil {
				return err
			}
			if err := v.(*Builder).WriteTo(w); err != nil {
				return err
			}
			if _, err := fmt.Fprintf(w, ")"); err != nil {
				return err
			}
		default:
			if _, err := fmt.Fprintf(w, "%s%s?", k, op); err != nil {
				return err
			}
			args = append(args, v)
		}
		if i != len(data)-1 {
			if _, err := fmt.Fprint(w, " AND "); err != nil {
				return err
			}
		}
		i = i + 1
	}
	w.Append(args...)
	return nil
}
type Lt map[string]interface{}
var _ Cond = Lt{}
func (lt Lt) WriteTo(w Writer) error {
	return WriteMap(w, lt, "<")
}
func (lt Lt) And(conds ...Cond) Cond {
	return condAnd{lt, And(conds...)}
}
func (lt Lt) Or(conds ...Cond) Cond {
	return condOr{lt, Or(conds...)}
}