def _check_ops(graph):
        """
        Returns the set of ops in @graph that are implemented, and the set
        for which no conversion function is registered. @graph can be
        either InternalTorchIRGraph or InternalTorchIRBlock.
        """
        implemented_ops = set()
        missing_ops = set()
        for node in graph.nodes:
            _add_op = _TORCH_OPS_REGISTRY.get_func(node.kind)
            if _add_op is None:
                missing_ops.add(node.kind)
            else:
                implemented_ops.add(node.kind)
            for block in node.blocks:
                _impl, _miss = TorchConverter._check_ops(block)
                implemented_ops.update(_impl)
                missing_ops.update(_miss)
        return implemented_ops, missing_ops

        Returns the set of ops in @graph that are implemented, and the set
        for which no conversion function is registered. @graph can be
        either InternalTorchIRGraph or InternalTorchIRBlock.
        
coremltools/converters/mil/frontend/torch/converter.py