'Acquire the desired quota, if any.
This is thread-safe, however will return None rather than block.
Args:
who: [string] Who is asking, for logging purposes.
quota: [dict] The desired quota for each keyed resource, if any.
Returns:
The quota acquired if successful, or None if not.'

def acquire_all_or_none_safe(self, who, quota):

    with self.__condition_variable:
        return self.acquire_all_or_none_unsafe(who, quota)
