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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 subtract_resources(res_a, res_b):
 """Return the resources remaining after subtracting res_b's resources from res_a. Parameters res_a : dict res_b : dict res_a. If A resource is not present in res_b, the value is presumed to be 0. """

    return {resource: value - res_b.get(resource, 0)
            for resource, value in iteritems(res_a)}