You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: custom_type_var_return_type.rs
    path of file: ./repos/ruff/crates/ruff_linter/src/rules/flake8_pyi/rules
    
    the code of the file until where you have to start completion: use ruff_diagnostics::{Diagnostic, Violation};
use ruff_macros::{derive_message_formats, violation};
use ruff_python_ast as ast;
use ruff_python_ast::helpers::map_subscript;
use ruff_python_ast::{Decorator, Expr, Parameters, TypeParam, TypeParams};
use
    
fn is_likely_private_typevar(type_var_name: &str, type_params: Option<&TypeParams>) -> bool {
    // Ex) `_T`
    if type_var_name.starts_with('_') {
        return true;
    }
    // Ex) `class Foo[T]: ...`
    type_params.is_some_and(|type_params| {
        type_params.iter().any(|type_param| {
            if let TypeParam::TypeVar(ast::TypeParamTypeVar { name, .. }) = type_param {
                name == type_var_name
            } else {
                false
            }
        })
    })
}