TODO docs.

def feet(kilometers=0, meters=0, miles=0, nautical=0):
    """
    TODO docs.
    """
    ret = 0.
    if nautical:
        kilometers += nautical / nm(1.)
    if meters:
        kilometers += meters / 1000.
    if kilometers:
        miles += mi(kilometers=kilometers)
    ret += miles * 5280
    return ret