def METHOD_NAME(self):
    c = self.get_cache()
    c["foo"] = ""
    c["bar"] = ""
    c["baz"] = ""
    c.filter(lambda p: p != "bar")  # only 'bar' is removed
    eq_(2, len(c))
    assert "foo" in c
    assert "baz" in c
    assert "bar" not in c