def get_fee(speed=FEE_SPEED_MEDIUM):
    """Gets the recommended satoshi per byte fee.

    :param speed: One of: 'fast', 'medium', 'slow'.
    :type speed: ``string``
    :rtype: ``int``
    """
    if speed == FEE_SPEED_FAST:
        return DEFAULT_FEE_FAST
    elif speed == FEE_SPEED_MEDIUM:
        return DEFAULT_FEE_MEDIUM
    elif speed == FEE_SPEED_SLOW:
        return DEFAULT_FEE_SLOW
    else:
        raise ValueError('Invalid speed argument.')
Gets the recommended satoshi per byte fee.

    :param speed: One of: 'fast', 'medium', 'slow'.
    :type speed: ``string``
    :rtype: ``int``