code: def make_oracle(input_qubits, output_qubit, x_bits):
      
      # Make oracle.
      # for (1, 1) it's just a Toffoli gate
      # otherwise negate the zero-bits.
      yield(cirq.X(q) for (q, bit) in zip(input_qubits, x_bits) if not bit)
      yield(cirq.TOFFOLI(input_qubits[0], input_qubits[1], output_qubit))
      yield(cirq.X(q) for (q, bit) in zip(input_qubits, x_bits) if not bit)
docs: Implement function {f(x) = 1 if x==x', f(x) = 0 if x!= x'}.