def METHOD_NAME(bindings, ret_value):
    """Make a nested let expressions.
    Parameters
    ----------
    bindings: List[Tuple[tvm.relay.Var,tvm.relay.Expr]]
        The sequence of let bindings
    ret_value: tvm.relay.Expr
        The final value of the expression.
    Returns
    -------
    lets: tvm.relay.Expr
        A nested let expression.
    """
    if ret_value is None:
        raise RuntimeError("ret is not called in this scope")
    if isinstance(ret_value, _expr.If) and ret_value.false_branch is None:
        raise RuntimeError("Creating an If expression without else.")
    let_expr = ret_value
    for var, value in reversed(bindings):
        let_expr = _expr.Let(var, value, let_expr)
    return let_expr