isNotPresent = const _NotPresentMatcher()

This instance is used to validate that a header or key does not exist.

When using hasResponse, hasHeaders or partial, this instance can be used as a value to indicate that a particular key should not exist. For example, the following would ensure that the evaluated map does not have the key 'foo':

    expect(map, partial({
      "id" : greaterThan(0),
      "foo" : isNotPresent
    });