docs: def mass_3d(self, r, kwargs, bool_list=None):
          """
          computes the mass within a 3d sphere of radius r
  
          :param r: radius (in angular units)
          :param kwargs: list of keyword arguments of lens model parameters matching the lens model classes
          :param bool_list: list of bools that are part of the output
          :return: mass (in angular units, modulo epsilon_crit)
          """
          bool_list = self._bool_list(bool_list)
          mass_3d = 0
          for i, func in enumerate(self.func_list):
              if bool_list[i] is True:
                  kwargs_i = {k:v for k, v in kwargs[i].items() if not k in ['center_x', 'center_y']}
                  mass_3d_i = func.mass_3d_lens(r, **kwargs_i)
                  mass_3d += mass_3d_i
                  #except:
                  #    raise ValueError('Lens profile %s does not support a 3d mass function!' % self.model_list[i])
          return mass_3d