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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 _initialize_counters(model_class, name, bases, attrs):
 """Stores the list of counter fields."""

    model_class._counters = []
    for k, v in attrs.iteritems():
        if isinstance(v, Counter):
            model_class._counters.append(k)