How to use the porespy.metrics.region_surface_areas function in porespy

def test_region_interface_areas(self):
        regions = self.regions
        areas = ps.metrics.region_surface_areas(regions)
        ia = ps.metrics.region_interface_areas(regions, areas)
        assert sp.all(ia.conns[0] == [2, 19])
        assert sp.around(ia.area[0], decimals=2) == 3.59

def test_region_surface_areas(self):
        regions = self.regions
        areas = ps.metrics.region_surface_areas(regions)
        assert not sp.any(sp.isnan(areas))

# -------------------------------------------------------------------------
    # Boundary Conditions
    regions = add_boundary_regions(regions=regions, faces=boundary_faces)
    # -------------------------------------------------------------------------
    # Padding distance transform and image to extract geometrical properties
    dt = pad_faces(im=dt, faces=boundary_faces)
    im = pad_faces(im=im, faces=boundary_faces)
    regions = regions*im
    regions = make_contiguous(regions)
    # -------------------------------------------------------------------------
    # Extract void and throat information from image
    net = regions_to_network(im=regions, dt=dt, voxel_size=voxel_size)
    # -------------------------------------------------------------------------
    # Extract marching cube surface area and interfacial area of regions
    if marching_cubes_area:
        areas = region_surface_areas(regions=regions)
        interface_area = region_interface_areas(regions=regions, areas=areas,
                                                voxel_size=voxel_size)
        net['pore.surface_area'] = areas * voxel_size**2
        net['throat.area'] = interface_area.area
    # -------------------------------------------------------------------------
    # Find void to void connections of boundary and internal voids
    boundary_labels = net['pore.label'] > b_num
    loc1 = net['throat.conns'][:, 0] < b_num
    loc2 = net['throat.conns'][:, 1] >= b_num
    pore_labels = net['pore.label'] <= b_num
    loc3 = net['throat.conns'][:, 0] < b_num
    loc4 = net['throat.conns'][:, 1] < b_num
    net['pore.boundary'] = boundary_labels
    net['throat.boundary'] = loc1 * loc2
    net['pore.internal'] = pore_labels
    net['throat.internal'] = loc3 * loc4

# -------------------------------------------------------------------------
    # For only one phase extraction with boundary regions
    phases_num = sp.unique(im).astype(int)
    phases_num = sp.trim_zeros(phases_num)
    if len(phases_num) == 1:
        if f is not None:
            snow.im = pad_faces(im=snow.im, faces=f)
        regions = regions * (snow.im.astype(bool))
        regions = make_contiguous(regions)
    # -------------------------------------------------------------------------
    # Extract N phases sites and bond information from image
    net = regions_to_network(im=regions, dt=dt, voxel_size=voxel_size)
    # -------------------------------------------------------------------------
    # Extract marching cube surface area and interfacial area of regions
    if marching_cubes_area:
        areas = region_surface_areas(regions=regions)
        interface_area = region_interface_areas(regions=regions, areas=areas,
                                                voxel_size=voxel_size)
        net['pore.surface_area'] = areas * voxel_size ** 2
        net['throat.area'] = interface_area.area
    # -------------------------------------------------------------------------
    # Find interconnection and interfacial area between ith and jth phases
    net = add_phase_interconnections(net=net, snow_partitioning_n=snow,
                                     marching_cubes_area=marching_cubes_area,
                                     alias=al)
    # -------------------------------------------------------------------------
    # label boundary cells
    net = label_boundary_cells(network=net, boundary_faces=f)
    # -------------------------------------------------------------------------

    temp = _net_dict(net)
    temp.im = im.copy()

solid_region = solid_region * ~im
    regions = pore_region + solid_region
    b_num = sp.amax(regions)
    # -------------------------------------------------------------------------
    # Boundary Conditions
    regions = add_boundary_regions(regions=regions, faces=boundary_faces)
    # -------------------------------------------------------------------------
    # Padding distance transform to extract geometrical properties
    dt = pad_faces(im=dt, faces=boundary_faces)
    # -------------------------------------------------------------------------
    # Extract void,solid and throat information from image
    net = regions_to_network(im=regions, dt=dt, voxel_size=voxel_size)
    # -------------------------------------------------------------------------
    # Extract marching cube surface area and interfacial area of regions
    if marching_cubes_area:
        areas = region_surface_areas(regions=regions)
        interface_area = region_interface_areas(regions=regions, areas=areas,
                                                voxel_size=voxel_size)
        net['pore.surface_area'] = areas * voxel_size**2
        net['throat.area'] = interface_area.area
    # -------------------------------------------------------------------------
    # Find void to void, void to solid and solid to solid throat conns
    loc1 = net['throat.conns'][:, 0] < solid_num
    loc2 = net['throat.conns'][:, 1] >= solid_num
    loc3 = net['throat.conns'][:, 1] < b_num
    pore_solid_labels = loc1 * loc2 * loc3

    loc4 = net['throat.conns'][:, 0] >= solid_num
    loc5 = net['throat.conns'][:, 0] < b_num
    solid_solid_labels = loc4 * loc2 * loc5 * loc3

    loc6 = net['throat.conns'][:, 1] < solid_num

faces = [(int('left' in f)*3, int('right' in f)*3),
                     (int('front' in f)*3, int('back' in f)*3),
                     (int('top' in f)*3, int('bottom' in f)*3)]
        dt = sp.pad(dt, pad_width=faces, mode='edge')
        im = sp.pad(im, pad_width=faces, mode='edge')
    else:
        dt = dt
    regions = regions*im
    regions = make_contiguous(regions)
    # -------------------------------------------------------------------------
    # Extract void and throat information from image
    net = regions_to_network(im=regions, dt=dt, voxel_size=voxel_size)
    # -------------------------------------------------------------------------
    # Extract marching cube surface area and interfacial area of regions
    if marching_cubes_area:
        areas = region_surface_areas(regions=regions, voxel_size=voxel_size)
        net['pore.surface_area'] = areas
        interface_area = region_interface_areas(regions=regions, areas=areas,
                                                voxel_size=voxel_size)
        net['throat.area'] = interface_area.area
    # -------------------------------------------------------------------------
    # Find void to void connections of boundary and internal voids
    boundary_labels = net['pore.label'] > b_num
    loc1 = net['throat.conns'][:, 0] < b_num
    loc2 = net['throat.conns'][:, 1] >= b_num
    pore_labels = net['pore.label'] <= b_num
    loc3 = net['throat.conns'][:, 0] < b_num
    loc4 = net['throat.conns'][:, 1] < b_num
    net['pore.boundary'] = boundary_labels
    net['throat.boundary'] = loc1 * loc2
    net['pore.internal'] = pore_labels
    net['throat.internal'] = loc3 * loc4