func (e *HeaderMapEncoder) MapSetFields(k string, m FieldMarshaler) {
	e.Err = fmt.Errorf("header map encoder MapSetFields not supported, %s", k)
}
MapSetFields Is not implemented, query map of FieldMarshaler is undefined.
package protocol
import (
	"fmt"
	"net/http"
)
type HeaderMapEncoder struct {
	Prefix string
	Header http.Header
	Err    error
}
func (e *HeaderMapEncoder) MapSetValue(k string, v ValueMarshaler) {
	if e.Err != nil {
		return
	}
	str, err := v.MarshalValue()
	if err != nil {
		e.Err = err
		return
	}
	if len(e.Prefix) > 0 {
		k = e.Prefix + k
	}
	e.Header.Set(k, str)
}
func (e *HeaderMapEncoder) List(k string) ListEncoder {
	if e.Err != nil {
		return nil
	}
	if len(e.Prefix) > 0 {
		k = e.Prefix + k
	}
	return &HeaderListEncoder{Key: k, Header: e.Header}
}
func (e *HeaderMapEncoder) Map(k string) MapEncoder {
	if e.Err != nil {
		return nil
	}
	if len(e.Prefix) > 0 {
		k = e.Prefix + k
	}
	return &HeaderMapEncoder{Prefix: k, Header: e.Header}
}
func (e *HeaderMapEncoder) Start() {}
func (e *HeaderMapEncoder) End() {}