code: def validate_before(self, content, file_to_handle):
          
          logger.debug('Looking for required strings: %s', self.must_include)
          included = True
          for string in self.must_include:
              if not re.search(r'{0}'.format(string), content):
                  logger.error('Required string `%s` not found in %s',
                               string, file_to_handle)
                  included = False
          if not included:
              logger.debug('Required strings not found')
              return False
          logger.debug('Required strings found')
          return True
docs: Verify that all required strings are in the file