Test:

        >>> cache = Cache(log_level=logging.WARNING)
        >>> cache.put('a', 0)
        >>> cache.pop('a')
        0
        >>> cache.pop('b') == None
        True

def pop(self, key, timeout=1, is_async=False, only_read=False):
        """
        Test:

        >>> cache = Cache(log_level=logging.WARNING)
        >>> cache.put('a', 0)
        >>> cache.pop('a')
        0
        >>> cache.pop('b') == None
        True
        """
        if key not in self.cache_items:
            return None
        return self.cache_items.pop(key)[key]