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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 sum(context, key, value, multiplier=1):
 """ Adds the given value to the total value currently held in ``key``. Use the multiplier if you want to turn a positive value into a negative and actually substract from the current total sum. Usage:: {% sum "MY_TOTAL" 42 -1 %} {{ MY_TOTAL }} """

    if key not in context.dicts[0]:
        context.dicts[0][key] = 0
    context.dicts[0][key] += value * multiplier
    return ''