def identifierScheme(identifier):
 if (identifier.startswith('xri://') or (identifier and (identifier[0] in XRI_AUTHORITIES))):
  return 'XRI'
 else:
  return 'URI'

def identifierScheme ( identifier ) : if ( identifier . startswith ( 'xri://' ) or ( identifier and ( identifier [ 0 ] in XRI_AUTHORITIES ) ) ) : return 'XRI' else : return 'URI'
determine if this identifier is an xri or uri .