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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 sub_map(self, counters_map):
 """Subtracts all counters from the map. For each counter in the passed map, subtracts its value to the counter in this map. Args: counters_map: CounterMap instance to subtract. """

    for counter_name in counters_map.counters:
      self.increment(counter_name, -counters_map.counters[counter_name])