def METHOD_NAME(self):
    density1 = 1.
    density2 = 2.
    # check with two shapes
    ek_species = self.make_default_ek_species()
    value_shape = tuple(ek_species.shape) + (1,)
    ek_species.add_boundary_from_shape(
        shape=self.wall_shape1, value=density1,
        boundary_type=espressomd.electrokinetics.DensityBoundary)
    ek_species.add_boundary_from_shape(
        shape=self.wall_shape2, value=density2 * np.ones(value_shape),
        boundary_type=espressomd.electrokinetics.DensityBoundary)
    self.check_boundary_flags(ek_species, "density", density1, density2)
    # check with union of two shapes
    ek_species = self.make_default_ek_species()
    union = espressomd.shapes.Union()
    union.add([self.wall_shape1, self.wall_shape2])
    ek_species.add_boundary_from_shape(
        shape=union, value=density1,
        boundary_type=espressomd.electrokinetics.DensityBoundary)
    self.check_boundary_flags(ek_species, "density", density1, density1)