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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 cuboid(target, throat_diameter='throat.diameter', throat_length='throat.length'):
 r""" Calculate surface area for a cuboid throat Parameters target : OpenPNM Object The object which this model is associated with. This controls the length of the calculated array, and also provides access to other necessary properties. throat_diameter : string Dictionary key to the throat diameter array. Default is 'throat.diameter'. throat_length : string Dictionary key to the throat length array. Default is 'throat.length'. """

    D = target[throat_diameter]
    L = target[throat_length]
    value = 4*D*L
    return value