import re


def is_valid_node_name(name):
    """
    Return True if the string is a valid Python identifier in lower ASCII range, False otherwise.

    The regular expression match pattern is r"^[a-z_][a-z0-9_]*".
    """
    return isinstance(name, str) and name.isidentifier() and re.fullmatch(r"^[a-z_][a-z\d_]*", name) is not None