def _mixture_(self) -> Sequence[tuple[float, Any]] | NotImplementedType:
        """Decompose into a probability distribution of unitaries.

        This method is used by the global `cirq.mixture` method.

        A mixture is described by an iterable of tuples of the form

            (probability of unitary, unitary as numpy array)

        The probability components of the tuples must sum to 1.0 and be between
        0 and 1 (inclusive).

        Returns:
            A list of (probability, unitary) pairs.
        """
Decompose into a probability distribution of unitaries.

        This method is used by the global `cirq.mixture` method.

        A mixture is described by an iterable of tuples of the form

            (probability of unitary, unitary as numpy array)

        The probability components of the tuples must sum to 1.0 and be between
        0 and 1 (inclusive).

        Returns:
            A list of (probability, unitary) pairs.
        
cirq-core/cirq/protocols/mixture_protocol.py