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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_default_prefix(self, instance=None):
 """Gets the prefix for this form. :param instance: the form model instance. When calling this method directly this should almost always stay None so it looks for self.instance. """

        if instance is None and hasattr(self, 'instance'):
            instance = self.instance

        if instance and instance.id is not None:
            # it's an existing instance, use the instance prefix
            instance_prefix = self.default_instance_prefix
            if instance_prefix is None:
                instance_prefix = self.__class__.__name__.lower() + 'i-'

            return '{0}{1}'.format(instance_prefix,
                                   instance.id)

        if self.default_new_prefix is not None:
            return self.default_new_prefix

        return self.__class__.__name__.lower() + 'new-'