code: def sign(message, **config):
      
  
      if not _implementation:
          init(**config)
  
      return _implementation.sign(message, **config)
docs: Insert two new fields into the message dict and return it.
  
      Those fields are:
  
          - 'signature' - the computed message digest of the JSON repr.
          - 'certificate' - the base64 certificate or gpg key of the signator.