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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _validate_header(self, hed):
 """ Validate the list that represents the table header. :param hed: The list that represents the table header. :type hed: list(list(hatemile.util.html.htmldomelement.HTMLDOMElement)) :return: True if the table header is valid or False if the table header is not valid. :rtype: bool """

        # pylint: disable=no-self-use

        if not bool(hed):
            return False
        length = -1
        for row in hed:
            if not bool(row):
                return False
            elif length == -1:
                length = len(row)
            elif len(row) != length:
                return False
        return True