def preprocess_transformers(self) -> list[cirq.TRANSFORMER]:
        """List of transformers which should be run before decomposing individual operations."""
        reorder_transfomers = (
            [transformers.insertion_sort_transformer] if self._reorder_operations else []
        )
        return [
            create_transformer_with_kwargs(
                transformers.expand_composite,
                no_decomp=lambda op: protocols.num_qubits(op) <= self.num_qubits,
            ),
            *reorder_transfomers,
            create_transformer_with_kwargs(
                merge_k_qubit_gates.merge_k_qubit_unitaries,
                k=self.num_qubits,
                rewriter=lambda op: op.with_tags(self._intermediate_result_tag),
            ),
        ]
List of transformers which should be run before decomposing individual operations.
cirq-core/cirq/transformers/target_gatesets/compilation_target_gateset.py