code: def _el_orb_tuple(string):
      
      el_orbs = []
      for split in string.split(','):
          splits = split.split('.')
          el = splits[0]
          if len(splits) == 1:
              el_orbs.append(el)
          else:
              el_orbs.append((el, tuple(splits[1:])))
      return el_orbs
docs: Parse the element and orbital argument strings.
  
      The presence of an element without any orbitals means that we want to plot
      all of its orbitals.
  
      Args:
          string (`str`): The selected elements and orbitals in in the form:
              `"Sn.s.p,O"`.
  
      Returns:
          A list of tuples specifying which elements/orbitals to plot. The output
          for the above example would be:
  
              `[('Sn', ('s', 'p')), 'O']`