code: def value_axis(self):
          
          valAx_lst = self._chartSpace.valAx_lst
          if not valAx_lst:
              raise ValueError('chart has no value axis')
  
          idx = 1 if len(valAx_lst) > 1 else 0
          return ValueAxis(valAx_lst[idx])
docs: The |ValueAxis| object providing access to properties of the value
          axis of this chart. Raises |ValueError| if the chart has no value
          axis.