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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def pull(self, chars='all', cb=None, block=True):
 """Update the state of all my proxy objects from the real objects."""

        if block:
            deltas = self.handle('get_char_deltas', chars=chars)
            self._upd_caches(deltas)
            if cb:
                cb(deltas)
        else:
            return self._submit(self._pull_async, chars, cb)