code: def dir_param_valid(d):
      '''True if d is a string and it's an existing directory.'''
      r = True
      if not isinstance(d, str) :
          r = False
          raise TypeError
      if not os.path.isdir(d):
          r = False
          raise ValueError
      return f dir_param_valid(d):
      '''True if d is a string and it's an existing directory.'''
      r = True
      if not isinstance(d, str) :
          r = False
          raise TypeError
      if not os.path.isdir(d):
          r = False
          raise ValueError
      return r
docs: True if d is a string and it's an existing directory.