def METHOD_NAME(structure_a, structure_b):
    """Compare two StructureData objects A, B and return a delta (A - B) of the relevant properties."""
    delta = AttributeDict()
    delta.absolute = AttributeDict()
    delta.relative = AttributeDict()
    volume_a = structure_a.get_cell_volume()
    volume_b = structure_b.get_cell_volume()
    delta.absolute.volume = np.absolute(volume_a - volume_b)
    delta.relative.volume = np.absolute(volume_a - volume_b) / volume_a
    pos_a = np.array([site.position for site in structure_a.sites])
    pos_b = np.array([site.position for site in structure_b.sites])
    delta.absolute.pos = pos_a - pos_b
    site_vectors = [delta.absolute.pos[i, :] for i in range(delta.absolute.pos.shape[0])]
    a_lengths = np.linalg.norm(pos_a, axis=1)
    delta.absolute.pos_lengths = np.array([np.linalg.norm(vector) for vector in site_vectors])
    delta.relative.pos_lengths = np.array([np.linalg.norm(vector) for vector in site_vectors]) / a_lengths
    cell_lengths_a = np.array(structure_a.cell_lengths)
    delta.absolute.cell_lengths = np.absolute(cell_lengths_a - np.array(structure_b.cell_lengths))
    delta.relative.cell_lengths = np.absolute(cell_lengths_a - np.array(structure_b.cell_lengths)) / cell_lengths_a
    cell_angles_a = np.array(structure_a.cell_angles)
    delta.absolute.cell_angles = np.absolute(cell_angles_a - np.array(structure_b.cell_angles))
    delta.relative.cell_angles = np.absolute(cell_angles_a - np.array(structure_b.cell_angles)) / cell_angles_a
    return delta