Returns the string message for the given error code.

        Args:
          cls (JLinkDataErrors): the ``JLinkDataErrors`` 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.

def to_string(cls, error_code):
        """Returns the string message for the given error code.

        Args:
          cls (JLinkDataErrors): the ``JLinkDataErrors`` 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.
        """
        if error_code == cls.ERROR_UNKNOWN:
            return 'Unknown error.'
        elif error_code == cls.ERROR_NO_MORE_EVENTS:
            return 'There are no more available watchpoint units.'
        elif error_code == cls.ERROR_NO_MORE_ADDR_COMP:
            return 'No more address comparisons can be set.'
        elif error_code == cls.ERROR_NO_MORE_DATA_COMP:
            return 'No more data comparisons can be set.'
        elif error_code == cls.ERROR_INVALID_ADDR_MASK:
            return 'Invalid flags passed for the address mask.'
        elif error_code == cls.ERROR_INVALID_DATA_MASK:
            return 'Invalid flags passed for the data mask.'
        elif error_code == cls.ERROR_INVALID_ACCESS_MASK:
            return 'Invalid flags passed for the access mask.'
        return super(JLinkDataErrors, cls).to_string(error_code)