cdf
Returns the cumulative distribution function value at x for this Gumbel distribution.
The CDF has the double-exponential form exp(-exp(-z)), where z = (x - mu) / beta. This gives the probability that a random value from this distribution is less than or equal to x.
Return
the probability that a value is less than or equal to x, in the range [0, 1].
Parameters
x
the point at which to evaluate the cumulative probability.