Signer constructor
      
      Signer({ 
    
    
- required String region,
- AwsClientCredentials? credentials,
- AwsClientCredentialsProvider? credentialsProvider,
- Client? client,
- String? endpointUrl,
Implementation
Signer({
  required String region,
  _s.AwsClientCredentials? credentials,
  _s.AwsClientCredentialsProvider? credentialsProvider,
  _s.Client? client,
  String? endpointUrl,
}) : _protocol = _s.RestJsonProtocol(
        client: client,
        service: _s.ServiceMetadata(
          endpointPrefix: 'signer',
          signingName: 'signer',
        ),
        region: region,
        credentials: credentials,
        credentialsProvider: credentialsProvider,
        endpointUrl: endpointUrl,
      );