# File lib/sup/modes/edit-message-mode.rb, line 275
  def format_headers header
    header_lines = []
    headers = (FORCE_HEADERS + (header.keys - FORCE_HEADERS)).map do |h|
      lines = make_lines "#{h}:", header[h]
      lines.length.times { header_lines << h }
      lines
    end.flatten.compact
    [headers, header_lines]
  end