code: @Nonnull
    public PreprocessorContext setExcludeExtensions(@Nonnull @MustNotContainNull final List<String> extensions) {
      this.excludeExtensions = new HashSet<>(assertDoesntContainNull(extensions));
      return this;
    }
docs: Set comma separated list of file extensions to be excluded from preprocessing
  
  @param extensions a comma separated file extension list, it must not be null
  @return this preprocessor context