<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def colon():
 """Colon case. Match a colon ":" only if not preceeded by a digit. Mainly to prevent a cut in the middle of time notations e.g. 10:01 """

    return RegexBuilder(
        pattern_args=symbols.COLON,
        pattern_func=lambda x: r"(?<!\d){}".format(x)).regex