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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 get_electron_number(self, charge=0):
 """Return the number of electrons. Args: charge (int):
 Charge of the molecule. Returns: int: """

        atomic_number = constants.elements['atomic_number'].to_dict()
        return sum([atomic_number[atom] for atom in self['atom']]) - charge