Return a dictionary with gateway options. The result is used
    to provide arguments to __ssh_gateway_arguments method.

def __ssh_gateway_config_dict(gateway):
    '''
    Return a dictionary with gateway options. The result is used
    to provide arguments to __ssh_gateway_arguments method.
    '''
    extended_kwargs = {}
    if gateway:
        extended_kwargs['ssh_gateway'] = gateway['ssh_gateway']
        extended_kwargs['ssh_gateway_key'] = gateway['ssh_gateway_key']
        extended_kwargs['ssh_gateway_user'] = gateway['ssh_gateway_user']
        extended_kwargs['ssh_gateway_command'] = gateway['ssh_gateway_command']
    return extended_kwargs