input: Write a python function to split a pathname into components in a platform-neutral way.
  assert fullsplit('path/to/file') == ['path', 'to', 'file']
  assert fullsplit('another/path/to/something') == ['another', 'path', 'to', 'something']
  assert fullsplit('/absolute/path/to/file') == ['', 'absolute', 'path', 'to', 'file']
output: def fullsplit(pathname):
      import os
      components = []
      while True:
          head, tail = os.path.split(pathname)
          if head == pathname:  # root (e.g., '/', 'C:\\')
              components.insert(0, head)
              break
          elif tail == '':  # no more components
              break
          else:
              components.insert(0, tail)
              pathname = head
      return components