def METHOD_NAME(func: FuncDecl) -> str:
    assert not '_co_' in func.name
    assert func.return_type == 'int'
    assert func.args[0].type in ['BlockDriverState *', 'BdrvChild *',
                                 'BlockBackend *']
    subsystem, subname = func.name.split('_', 1)
    name = f'{subsystem}_co_{subname}'
    t = func.args[0].type
    if t == 'BlockDriverState *':
        bs = 'bs'
    elif t == 'BdrvChild *':
        bs = 'child->bs'
    else:
        bs = 'blk_bs(blk)'
    struct_name = snake_to_camel(name)
    return f"""\