<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def chk_fraction_digits_arg(s):
 """Checks if the string `s` is a valid fraction-digits argument. Return True or False."""

    try:
        v = int(s)
        if v >= 1 and v <= 18:
            return True
        else:
            return False
    except ValueError:
        return False