docs: def set_yaxis(self, param, unit=None, label=None):
          """ Sets the value of use on the yaxis
          :param param: value to use on the yaxis, should be a variable or function of the objects in objectList. ie 'R'
          for the radius variable and 'calcDensity()' for the calcDensity function
  
          :param unit: the unit to scale the values to
          :type unit: quantities unit or None
  
          :param label: axis label to use, if None "Parameter (Unit)" is generated here and used
          :type label: str
          """
          if unit is None:
              unit = self._getParLabelAndUnit(param)[1]  # use the default unit defined in this class
          self._yaxis_unit = unit
  
          self._yaxis = self._set_axis(param, unit)
          if label is None:
              self.ylabel = self._gen_label(param, unit)
          else:
              self.ylabel = label