docs: def min_volatility(self):
          """
          Minimise volatility.
  
          :return: asset weights for the volatility-minimising portfolio
          :rtype: dict
          """
          args = (self.cov_matrix, self.gamma)
          result = sco.minimize(
              objective_functions.volatility,
              x0=self.initial_guess,
              args=args,
              method="SLSQP",
              bounds=self.bounds,
              constraints=self.constraints,
          )
          self.weights = result["x"]
          return dict(zip(self.tickers, self.weights))