func (s SignatureType) IsAnonymous() bool {
	return s == SignatureAnonymous
}
IsAnonymous - is signature empty?
package credentials
import "strings"
type SignatureType int
const (
	SignatureDefault SignatureType = iota
	SignatureV4
	SignatureV2
	SignatureV4Streaming
	SignatureAnonymous  
)
func (s SignatureType) IsV2() bool {
	return s == SignatureV2
}
func (s SignatureType) IsV4() bool {
	return s == SignatureV4 || s == SignatureDefault
}
func (s SignatureType) IsStreamingV4() bool {
	return s == SignatureV4Streaming
}