code: def beta(self, val:float)->None:
          "Set beta (or alpha as makes sense for given optimizer)."
          if val is None: return
          if 'betas' in self.opt_keys:    self.set_val('betas', (self._mom, listify(val, self._beta)))
          elif 'alpha' in self.opt_keys:  self.set_val('alpha', listify(val, self._beta))
          self._beta = listify(val, self._betaf beta(self, val:float)->None:
          "Set beta (or alpha as makes sense for given optimizer)."
          if val is None: return
          if 'betas' in self.opt_keys:    self.set_val('betas', (self._mom, listify(val, self._beta)))
          elif 'alpha' in self.opt_keys:  self.set_val('alpha', listify(val, self._beta))
          self._beta = listify(val, self._beta)
docs: Set beta (or alpha as makes sense for given optimizer).