code: def enable_mfa_device(self,
                            user_name,
                            serial_number,
                            authentication_code_1,
                            authentication_code_2):
          
          user = self.get_user(user_name)
          if serial_number in user.mfa_devices:
              raise IAMConflictException(
                  "EntityAlreadyExists",
                  "Device {0} already exists".format(serial_number)
              )
  
          user.enable_mfa_device(
              serial_number,
              authentication_code_1,
              authentication_code_2
          )
docs: Enable MFA Device for user.