code: @PublicAPI(usage = ACCESS)
      public String getNamePart(int index) {
          checkArgument(index > 0 && index <= matchingGroups.size(), "Found no name part with index %d", index);
          return matchingGroups.get(index - 1);
      }
docs: Returns a matching part of this slice. E.g. if the slice was created by matching '..(*).controller.(*)..',
  against 'some.other.controller.here.more', then name part '1' would be 'other' and name part '2' would
  be 'here'.
  
  @param index The index of the matched group
  @return The part of the matched package name.