def __init__(self, prior_mu=None, prior_beta=None, prior_strength=1.0):
        """
        Gumbel distribution.

        https://en.wikipedia.org/wiki/Gumbel_distribution

        - Univariate continuous distribution
        - Support: :math:`\\mathbb{R}`.
        - Parameters: location :math:`\\mu \\in \\mathbb{R}` and scale :math:`\\beta > 0`.

        Parameters
        ----------
        prior_mu
            location :math:`\\mu` of the prior Gumbel distribution (default: None).
        prior_beta
            scale :math:`\\beta` of the prior Gumbel distribution (default: None).
        prior_strength
            strength of the loss regularisation induced by the prior
        """
        self.prior_mu = prior_mu
        self.prior_beta = prior_beta
        _check_strict_positive(self.prior_beta)
        self.softplus = nn.Softplus()
        super().__init__(
            likelihood_type=LikelihoodType.Gumbel,
            parameter_names=["mu", "beta"],
            prior_strength=prior_strength,
        )

        Gumbel distribution.

        https://en.wikipedia.org/wiki/Gumbel_distribution

        - Univariate continuous distribution
        - Support: :math:`\mathbb{R}`.
        - Parameters: location :math:`\mu \in \mathbb{R}` and scale :math:`\beta > 0`.

        Parameters
        ----------
        prior_mu
            location :math:`\mu` of the prior Gumbel distribution (default: None).
        prior_beta
            scale :math:`\beta` of the prior Gumbel distribution (default: None).
        prior_strength
            strength of the loss regularisation induced by the prior
        
darts/utils/likelihood_models/torch.py