docs: def deriv(self, p):
          """
          Derivative of the power transform
  
          Parameters
          ----------
          p : array-like
              Mean parameters
  
          Returns
          --------
          g'(p) : array
              Derivative of power transform of `p`
  
          Notes
          -----
          g'(`p`) = `power` * `p`**(`power` - 1)
          """
          return self.power * np.power(p, self.power - 1)