Tuning initial slice width parameter

def tune(self, verbose=None):
        """
        Tuning initial slice width parameter
        """
        if not self._tune:
            return False
        else:
            self.w_tune.append(
                abs(self.stochastic.last_value - self.stochastic.value))
            self.w = 2 * (sum(self.w_tune) / len(self.w_tune))
            return True