code: def verify_header(self, key, val):
          
  
          if isinstance(val, list):
              if self.headers[key] in val:
                  return True
              else:
                  return False
          else:
              if self.headers[key] == val:
                  return True
              else:
                  return False
docs: Check that a particular header claim is present and has a specific value
  
          :param key: The claim
          :param val: The value of the claim
          :raises: KeyError if the claim is not present in the header
          :return: True if the claim exists in the header and has the prescribed
              value