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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_timestamps(self):
 """ Verifies that the document is valid according to Conditions Element :returns: True if the condition is valid, False otherwise :rtype: bool """

        conditions_nodes = self.__query_assertion('/saml:Conditions')

        for conditions_node in conditions_nodes:
            nb_attr = conditions_node.get('NotBefore')
            nooa_attr = conditions_node.get('NotOnOrAfter')
            if nb_attr and OneLogin_Saml2_Utils.parse_SAML_to_time(nb_attr) > OneLogin_Saml2_Utils.now() + OneLogin_Saml2_Constants.ALLOWED_CLOCK_DRIFT:
                raise OneLogin_Saml2_ValidationError(
                    'Could not validate timestamp: not yet valid. Check system clock.',
                    OneLogin_Saml2_ValidationError.ASSERTION_TOO_EARLY
                )
            if nooa_attr and OneLogin_Saml2_Utils.parse_SAML_to_time(nooa_attr) + OneLogin_Saml2_Constants.ALLOWED_CLOCK_DRIFT <= OneLogin_Saml2_Utils.now():
                raise OneLogin_Saml2_ValidationError(
                    'Could not validate timestamp: expired. Check system clock.',
                    OneLogin_Saml2_ValidationError.ASSERTION_EXPIRED
                )
        return True