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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 _slice_match_level(self, overlay_items):
 """ Find the match strength for a list of overlay items that must be exactly the same length as the pattern specification. """

        level = 0
        for spec, el in zip(self._pattern_spec, overlay_items):
            if spec[0] != type(el).__name__:
                return None
            level += 1      # Types match
            if len(spec) == 1: continue

            group = [el.group, group_sanitizer(el.group, escape=False)]
            if spec[1] in group: level += 1  # Values match
            else:                     return None

            if len(spec) == 3:
                group = [el.label, label_sanitizer(el.label, escape=False)]
                if (spec[2] in group):
                    level += 1  # Labels match
                else:
                    return None
        return level