'Return a 2-tuple of the units value and the units name. Automatically
determine whether to return the linear or angular units.'

@property
def units(self):

    (units, name) = (None, None)
    if (self.projected or self.local):
        (units, name) = capi.linear_units(self.ptr, byref(c_char_p()))
    elif self.geographic:
        (units, name) = capi.angular_units(self.ptr, byref(c_char_p()))
    if (name is not None):
        name = force_text(name)
    return (units, name)
