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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 prepare_value(self, value):
 """ To avoid evaluating the lazysorted callable more than necessary to establish a potential initial value for the field, we do it here. If there's - only one template choice, and - the field is required, and - there's no prior initial set (either by being bound or by being set higher up the stack then forcibly select the only "good" value as the default. """

        if value is None and self.required:
            choices =list(self.choices)
            if len(choices) == 1:
                value = choices[0][0]
        return super(TemplateChoiceField, self).prepare_value(value)