code: def thumbnail_preview(src_path):
    ''' Returns the path to small thumbnail preview. '''
    try:
      assert(exists(src_path))
  
      width = '1980'
  
      dest_dir = mkdtemp(prefix='pyglass')
      cmd = [QLMANAGE, '-t', '-s', width, src_path, '-o', dest_dir]
      assert(check_call(cmd) == 0)
  
      src_filename = basename(src_path)
      dest_list = glob(join(dest_dir, '%s.png' % (src_filename)))
      assert(dest_list)
  
      dest_path = dest_list[0]
      assert(exists(dest_path))
  
      return dest_path
    except:
      return Nonf thumbnail_preview(src_path):
    ''' Returns the path to small thumbnail preview. '''
    try:
      assert(exists(src_path))
  
      width = '1980'
  
      dest_dir = mkdtemp(prefix='pyglass')
      cmd = [QLMANAGE, '-t', '-s', width, src_path, '-o', dest_dir]
      assert(check_call(cmd) == 0)
  
      src_filename = basename(src_path)
      dest_list = glob(join(dest_dir, '%s.png' % (src_filename)))
      assert(dest_list)
  
      dest_path = dest_list[0]
      assert(exists(dest_path))
  
      return dest_path
    except:
      return None
docs: Returns the path to small thumbnail preview.