':param child_policy: an instantiated :class:`.LoadBalancingPolicy`
that this one will defer to.
:param predicate: a one-parameter function that takes a :class:`.Host`.
If it returns a falsey value, the :class:`.Host` will
be :attr:`.IGNORED` and not returned in query plans.'

def __init__(self, child_policy, predicate):

    super(HostFilterPolicy, self).__init__()
    self._child_policy = child_policy
    self._predicate = predicate
