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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 set_value_field(self, model, field_name):
 """ Adds a ``value`` field to this form that uses the appropriate formfield for the named target field. This will help to ensure that the value is correctly validated. """

        fields = fields_for_model(model, fields=[field_name])
        self.fields['value'] = fields[field_name]