import re


def to_snake_case(camel_case_str):
    """
    Returns `camel_case_str` (e.g. `SomeStr`) as snake_case (e.g. `some_str`)

    :param camel_case_str: A string in `CamelCase`
    :return: The string in `snake_case`
    """
    els = [
        el.lower()
        for el in re.findall("[a-zA-Z][^A-Z_]*", camel_case_str)
        if el != "_"
    ]
    return "_".join(els)