docs: def _find_basic_palette(result):
      ''' Find the platform-dependent 16-color basic palette.
  
          This is used for "downgrading to the nearest color" support.
      '''
      pal_name = 'default (xterm)'
      basic_palette = color_tables.xterm_palette4
      if env.SSH_CLIENT:  # fall back to xterm over ssh, info often wrong
          pal_name = 'ssh (xterm)'
      else:
          if os_name == 'nt':
              if sys.getwindowsversion()[2] > 16299: # Win10 FCU, new palette
                  pal_name = 'cmd_1709'
                  basic_palette = color_tables.cmd1709_palette4
              else:
                  pal_name = 'cmd_legacy'
                  basic_palette = color_tables.cmd_palette4
          elif sys.platform == 'darwin':
              if env.TERM_PROGRAM == 'Apple_Terminal':
                  pal_name = 'termapp'
                  basic_palette = color_tables.termapp_palette4
              elif env.TERM_PROGRAM == 'iTerm.app':
                  pal_name = 'iterm'
                  basic_palette = color_tables.iterm_palette4
          elif os_name == 'posix':
              if env.TERM in ('linux', 'fbterm'):
                  pal_name = 'vtrgb'
                  basic_palette = parse_vtrgb()
              elif env.TERM.startswith('xterm'):
                  # fix: LOW64 - Python on Linux on Windows!
                  if 'Microsoft' in os.uname().release:
                      pal_name = 'cmd_1709'
                      basic_palette = color_tables.cmd1709_palette4
                      result = 'truecolor'  # override
                  elif sys.platform.startswith('freebsd'):  # vga console :-/
                      pal_name = 'vga'
                      basic_palette = color_tables.vga_palette4
                  else:
                      try:  # TODO: check green to identify palette, others?
                          if get_color('index', 2)[0][:2] == '4e':
                              pal_name = 'tango'
                              basic_palette = color_tables.tango_palette4
                          else:
                              raise RuntimeError('not the color scheme.')
                      except (IndexError, RuntimeError):
                          pass
          else:  # Amiga/Atari :-P
              log.warn('Unexpected OS: os.name: %s', os_name)
  
      return result, pal_name, basic_palette