text: import mimetypes
  import os
  
  from typing import Dict, Optional
  
  
  def merge_dicts(dict_a: Dict, dict_b: Dict) -> Dict:
      """Merge two dictionaries.
  
      Arguments:
          dict_a (dict): The dictionary to use as the base.
          dict_b (dict): The dictionary to update the values with.
  
      Returns:
          dict: A new merged dictionary.
  
      """
      dict_z = dict_a.copy()
      dict_z.update(dict_b)
      return dict_z
  
  
  def guess_mime(path: str) -> Optional[str]:
      """Guess the mime type for a given path.
  
      Arguments:
          root (str): the root path of the file tree
          path (str): the sub-path within the file tree
  
      Returns:
          str: the guessed mime-type
  
      """
      mtypes = mimetypes.guess_type(path)
      ftype = None
      if os.path.isdir(path):
          ftype = "directory"
      elif os.access(path, os.F_OK) and mtypes[0]:
          ftype = mtypes[0]
      else:
          ftype = "application/octet-stream"
      return ftype
  