# File lib/fog/aws/requests/sts/assume_role.rb, line 29
        def assume_role(role_session_name, role_arn, external_id=nil, policy=nil, duration=3600)
          request({
            'Action'          => 'AssumeRole',
            'RoleSessionName' => role_session_name,
            'RoleArn'         => role_arn,
            'Policy'          => policy && Fog::JSON.encode(policy),
            'DurationSeconds' => duration,
            'ExternalId'      => external_id,
            :idempotent       => true,
            :parser           => Fog::Parsers::AWS::STS::AssumeRole.new
          })
        end