def __init__(self, p: float, gamma: float) -> None:
        r"""The generalized amplitude damping channel.

        Args:
            p: the probability of the environment being not excited
            gamma: the probability of energy transfer

        Raises:
            ValueError: if gamma or p is not a valid probability.
        """
        self._p = value.validate_probability(p, 'p')
        self._gamma = value.validate_probability(gamma, 'gamma')
The generalized amplitude damping channel.

        Args:
            p: the probability of the environment being not excited
            gamma: the probability of energy transfer

        Raises:
            ValueError: if gamma or p is not a valid probability.
        
cirq-core/cirq/ops/common_channels.py