code: def to_string(cls, error_code):
          
          if error_code == cls.COMPARE_ERROR:
              return 'Error comparing flash content to programming data.'
          elif error_code == cls.PROGRAM_ERASE_ERROR:
              return 'Error during program/erase phase.'
          elif error_code == cls.VERIFICATION_ERROR:
              return 'Error verifying programmed data.'
          return super(JLinkFlashErrors, cls).to_string(error_code)
docs: Returns the string message for the given ``error_code``.
  
          Args:
            cls (JLinkFlashErrors): the ``JLinkFlashErrors`` class
            error_code (int): error code to convert
  
          Returns:
            An error string corresponding to the error code.
  
          Raises:
            ValueError: if the error code is invalid.