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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 to_lower(cls):
 # NOQA """ Return a list of all the fields that should be lowercased This is done on fields with `lower=True`. """


        email = cls.get_fields_by_class(EmailType)
        lower = cls.get_fields_by_prop('lower', True) + email

        return list(set(email + lower))