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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 PhenomModel(self, r):
 """Fit to field map A phenomenological fit by Ryan Bayes (Glasgow) to a field map generated by Bob Wands (FNAL). It assumes a 1 cm plate. This is dated January 30th, 2012. Not defined for r <= 0"""

        if r <= 0:
            raise ValueError
        field = self.B0 + self.B1 * G4.m / r + self.B2 * math.exp(-1 * self.H * r / G4.m)
        return field