docs: def random(self, filetype, **kwargs):
          ''' Returns random number of the given type of file
  
          Parameters
          ----------
          filetype : str
              File type parameter.
  
          num : int
              The number of files to return
  
          as_url: bool
              Boolean to return SAS urls
  
          refine: str
              Regular expression string to filter the list of files by
              before random selection
  
          Returns
          -------
          random : list
              Random file selected from the expanded list of full paths on disk.
  
          '''
          expanded_files = self.expand(filetype, **kwargs)
          isany = self.any(filetype, **kwargs)
          if isany:
              # get the desired number
              num = kwargs.get('num', 1)
              assert num <= len(expanded_files), 'Requested number must be larger the sample.  Reduce your number.'
              return sample(expanded_files, num)
          else:
              return None