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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 add_attribute_model(self, name, # type: str attr, # type: AttributeModel writeable_func=None, # type: Optional[Callable] ):
 """Register a pre-existing AttributeModel to be added to the Block"""

        return self._field_registry.add_attribute_model(
            name, attr, writeable_func, self._part)