Parse `nni.function_choice` expression.
    Return the AST node of annotated expression and a list of dumped function call expressions.
    code: annotation string

def parse_nni_function(code):
    """Parse `nni.function_choice` expression.
    Return the AST node of annotated expression and a list of dumped function call expressions.
    code: annotation string
    """
    name, call = parse_annotation_function(code, 'function_choice')
    funcs = [ast.dump(func, False) for func in call.args]
    convert_args_to_dict(call, with_lambda=True)

    name_str = astor.to_source(name).strip()
    call.keywords[0].value = ast.Str(s=name_str)

    return call, funcs