'Remove this host from the internal list of usable hosts in the label.
This is provided as an optimization -- when code gets a host from a
label and concludes it\'s unusable, it can call this to avoid getting
that host again in the future (within this tick).  This function should
not affect correctness.'

def remove_host_from_label(self, host_id, label_id):

    raise NotImplementedError
