def check_id(string):
    """ Runs a basic check for things that look like ID numbers.
    Currently, simply checks to see that numerals outnumber
    other types of characters, and that the string is probably
    long enough to contain an ID."""
    string = string.strip()
    if len(string) == 0 or len(string) < 4:
        return 0.0
    count = 0.0
    for c in string:
        if c.isdigit():
            count += 1
    if count / len(string) > 0.5:
        return count/len(string)
    else:
        return None