code: def main(argv=None):
      
      # Get command line arguments, validate them, and normalize them
      opts = cmdparse.parse_args(argv)
      assert validate_opts.validate(opts)
      opts = normalize_opts.normalize(opts)
  
      if opts.verbose:
          # Update client: print input and output directories
          messages.print_input_output(opts)
  
      file_paths = fileparse.get_file_list(opts)
      assert validate_files.validate(file_paths, opts)
  
      if opts.verbose and opts.is_dir:
          # Update client: print files that will be parsed
          messages.print_files(opts, file_paths)
  
      # For now, only using default GitHub Markdown for parsing
      # Collect tag/anchor combinations
      collector = make_github_markdown_collector(opts)
      anchors, duplicate_tags = collector.collect(file_paths)
      assert validate_anchors.validate(anchors, duplicate_tags, opts)
  
      # Write files using previously found AnchorHub tags and generated anchors
      writer = make_github_markdown_writer(opts)
      counter = writer.write(file_paths, anchors, opts)
  
      if opts.verbose:
          if opts.is_dir:
              # Update client: print files that had modifications
              messages.print_modified_files(opts, anchors)
          # Print summary statistics
          messages.print_summary_stats(counter)
docs: Main entry method for AnchorHub. Takes in command-line arguments,
      finds files to parse within the specified input directory, and outputs
      parsed files to the specified output directory.
  
      :param argv: a list of string command line arguments