# File lib/asciidoctor/extensions.rb, line 636
    def initialize groups = {}
      @groups = groups
      @preprocessor_extensions = @tree_processor_extensions = @postprocessor_extensions = @include_processor_extensions = @docinfo_processor_extensions = nil
      @block_extensions = @block_macro_extensions = @inline_macro_extensions = nil
      @document = nil
    end