def _isSubRange(value):
    """
    Check if the input string represents a valid subRange.

    Return a tuple, first element in the tuple is a boolean tells the validation result, while
    the second element contains the error message if there is one.
    """
    contents = value.split("-")
    if len(contents) != 2:
        return False, "Invalid subRange: {}".format(value)
    try:
        int(contents[0])
    except ValueError:
        return False, "Invalid subRange start: {}".format(contents[0])
    try:
        int(contents[1])
    except ValueError:
        return False, "Invalid subRange end: {}".format(contents[1])
    return True, None