docs: def _get_label(self):
          '''Find the label for the output files 
           for this calculation
          '''
          if self._label is None:
              foundfiles = False
              for f in self._files:
                  if ".files" in f: 
                      foundfiles = True
                      self._label = f.split(".")[0]
                      with open(self._label + '.files', 'r') as fp:
                          line = fp.readline().split()[0]
                          if line != self._label + ".in":
                             fp.close()
                             raise Exception('first line must be label.in')
                          line = fp.readline().split()[0]
                          if line != self._label + ".txt":
                             fp.close()
                             raise Exception('second line must be label.txt')
                          line = fp.readline().split()[0]
                          if line != self._label + "i":
                             fp.close()
                             raise Exception('third line must be labeli')
                          line = fp.readline().split()[0]
                          if line != self._label + "o":
                             fp.close()
                             raise Exception('fourth line must be labelo')
                          fp.close()
              if foundfiles:
                  return self._label
              else:
                  raise Exception('label.files not found')
                                  
  #ASE format
  #        (self.prefix + '.in') # input
  #        (self.prefix + '.txt')# output
  #        (self.prefix + 'i')   # input
  #        (self.prefix + 'o')   # output
                  
          else:
              return self._label