code: def access_key(self):
          
          credential = self.query_parameters.get(_x_amz_credential)
          if credential is not None:
              credential = url_unquote(credential[0])
          else:
              credential = self.authorization_header_parameters.get(_credential)
  
              if credential is None:
                  raise AttributeError("Credential was not passed in the request")
          try:
              key, scope = credential.split("/", 1)
          except ValueError:
              raise AttributeError("Invalid request credential: %r" % credential)
  
          if scope != self.credential_scope:
              raise AttributeError("Incorrect credential scope: %r (wanted %r)" %
                                   (scope, self.credential_scope))
  
          return key
docs: The access key id used to sign the request.
  
          If the access key is not in the same credential scope as this request,
          an AttributeError exception is raised.