func (f *Filter) MarshalJSON() ([]byte, error) {
	m := make(map[string]interface{})
	m["field"] = f.Field
	m["operator"] = f.Op
	m["value"] = f.Value
	return json.Marshal(m)
}
MarshalJSON marshals the Filter as JSON data.
package ud859
import (
	"encoding/json"
	"fmt"
	"strconv"
	"time"
	"github.com/GoogleCloudPlatform/go-endpoints/endpoints"
)
const (
	EQ  = "="
	LT  = "<"
	GT  = ">"
	LTE = "<="
	GTE = ">="
	NE  = "!="
)
const (
	Name           = "NAME"
	City           = "CITY"
	Topics         = "TOPIC"
	StartDate      = "START_DATE"
	EndDate        = "END_DATE"
	Month          = "MONTH"
	MaxAttendees   = "MAX_ATTENDEES"
	SeatsAvailable = "SEATS_AVAILABLE"
)
func errConflict(message string) error {
	return endpoints.NewConflictError("ud859: %s", message)
}
func errInternalServer(cause error, message string) error {
	return endpoints.NewInternalServerError("ud859: %s (%v)", message, cause)
}
func errUnauthorized(cause error, message string) error {
	return endpoints.NewUnauthorizedError("ud859: %s (%v)", message, cause)
}
func errBadRequest(cause error, message string) error {
	return endpoints.NewBadRequestError("ud859: %s (%v)", message, cause)
}
func errNotFound(cause error, message string) error {
	return endpoints.NewNotFoundError("ud859: %s (%v)", message, cause)
}