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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 reaction_charge(reaction, compound_charge):
 """Calculate the overall charge for the specified reaction. Args: reaction: :class:`psamm.reaction.Reaction`. compound_charge: a map from each compound to charge values. """


    charge_sum = 0.0
    for compound, value in reaction.compounds:
        charge = compound_charge.get(compound.name, float('nan'))
        charge_sum += charge * float(value)
    return charge_sum