human
Define a custom two-qubit gate."""
class AnotherGate(cirq.Gate):
    def __init__(self):
        super(AnotherGate, self)

    def _num_qubits_(self):
        return 2
    
    def _unitary_(self):
        return np.array([
            [1.0, -1.0, 0.0,  0.0],
            [0.0,  0.0, 1.0,  1.0],
            [1.0,  1.0, 0.0,  0.0],
            [0.0,  0.0, 1.0, -1.0]
        ]) / np.sqrt(2)
    
    def _circuit_diagram_info_(self, args):
        return "Top wire symbol", "Bottom wire symbol"

this_gate = AnotherGate()
Given the above code, generate some markdown instructions for it.

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Give me a code to define a custom two-qubit gate?
assistant
#Here is code to define a custom two-qubit gate.

An alternative to inheriting from cirq.Gate is to inherit from cirq.SingleQubitGate, in which case defining _num_qubits_ is unnecessary. An example of a defining a two-qubit gate is shown below.