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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 get_value_prob(self, attr_name, value):
 """ Returns the value probability of the given attribute at this node. """

        if attr_name not in self._attr_value_count_totals:
            return
        n = self._attr_value_counts[attr_name][value]
        d = self._attr_value_count_totals[attr_name]
        return n/float(d)