def __calculate_bu_dfs(dfs_data):
u = dfs_data['<STR_LIT>'][<NUM_LIT:0>]<EOL>b = {}<EOL>b[u] = D(u, dfs_data)<EOL>__calculate_bu_dfs_recursively(u, b, dfs_data)<EOL>return b<EOL>
Calculates the b(u) lookup table.