code: function getSignerClass(request) {
      var version;
      // get operation authtype if present
      var operation = null;
      var authtype = '';
      if (request) {
        var operations = request.service.api.operations || {};
        operation = operations[request.operation] || null;
        authtype = operation ? operation.authtype : '';
      }
      if (this.config.signatureVersion) {
        version = this.config.signatureVersion;
      } else if (authtype === 'v4' || authtype === 'v4-unsigned-body') {
        version = 'v4';
      } else {
        version = this.api.signatureVersion;
      }
      return AWS.Signers.RequestSigner.getVersion(version);
    }
docs: Gets the signer class for a given request
  @api private