docs: def build_expected(dynamizer, expected):
      """ Build the Expected parameters from a dict """
      ret = {}
      for k, v in six.iteritems(expected):
          if is_null(v):
              ret[k] = {
                  'Exists': False,
              }
          else:
              ret[k] = {
                  'Exists': True,
                  'Value': dynamizer.encode(v),
              }
      return ret