code: def extract(self, dest_fldr, password=''):
          
          #print('extracting to ' + dest_fldr)
          if self.type == 'ZIP':
              self._extract_zip(dest_fldr, password)
          elif self.type == 'GZ':
              self._extract_gz(dest_fldr, password)
          elif self.type == 'TAR':
              self._extract_tar(dest_fldr, self.fname)
          else:
              raise('Unknown archive file type')
docs: unzip the file contents to the dest_folder
          (create if it doesn't exist)
          and then return the list of files extracted