code: def validate_timestamps(self):
          
          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
docs: Verifies that the document is valid according to Conditions Element
  
          :returns: True if the condition is valid, False otherwise
          :rtype: bool