# Functions
NewMetadataNotRecognizedError will create a new MetadataUnrecognizedError.
NewPairRequiredError will create a new PairRequiredError.
NewPairUnsupportedError will create a new PairUnsupportedError.
# Variables
ErrCapabilityInsufficient means this service doesn't have this capability.
ErrObjectNotExist means the object to be operated is not exist.
ErrPermissionDenied means this operation doesn't have enough permission.
ErrRestrictionDissatisfied means this operation doesn't meat service's restriction.
# Structs
InitError means this service init failed.
MetadataUnrecognizedError means this operation meets unrecognized metadata.
PairRequiredError means this operation has required pair but missing.
PairUnsupportedError means this operation has unsupported pair.
ServiceError represent errors related to service.
StorageError represent errors related to storage.