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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def build_re_pattern_from_intervals(intervals: IntervalListType) -> BuiltInReType: """ Convert intervals to regular expression pattern. :param intervals: Unicode codepoint intervals. """


    inner = [f'{chr(lb)}-{chr(ub)}' for lb, ub in intervals]
    joined_inner = ''.join(inner)
    pattern = f'[{joined_inner}]+'

    return re.compile(pattern, re.UNICODE)