def _energy_difference(newEnergy, oldEnergy):
    diff = {}
    for key in newEnergy:
        if key in oldEnergy:
            diff[key] = newEnergy[key] - oldEnergy[key]
    return diff
returns a dict with (newEnergy - oldEnergy) for each type (=key) of energy,
dataset/ETHPy150Open sosy-lab/benchexec/benchexec/util.py/_energy_difference