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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_defaults(self):
 """ Set default values to fields. We assume that they are not yet populated as this method is called just after creation of a new pk. """

        for field_name in self._fields:
            if field_name in self._init_fields:
                continue
            field = self.get_field(field_name)
            if hasattr(field, "default"):
                field.proxy_set(field.default)