def to_bool(value, do_raise=True):
        """Convert a string to a boolean value.

        If the string consists of digits, the integer value of the string
        is coerced to a boolean value.  Otherwise, any of the strings "t",
        "true", "on", "y", and "yes" are considered True and any of the
        strings "f", "false", "off", "n", and "no" are considered False.
        A ValueError will be raised for any other value.
        """

        value = value.lower()

        # Try it as an integer
        if value.isdigit():
            return bool(int(value))

        # OK, check it against the true/false values...
        if value in _str_true:
            return True
        elif value in _str_false:
            return False

        # Not recognized
        if do_raise:
            raise ValueError("invalid literal for to_bool(): %r" % value)

        return False