code: def preprocess(self, style):
          
          if self.property == 'font':
              style = [
                  ''.join(u.expression()) if hasattr(u, 'expression') else u
                  for u in style
              ]
          else:
              style = [(u, ' ') if hasattr(u, 'expression') else u
                       for u in style]
          return style
docs: Hackish preprocessing from font shorthand tags.
          Skips expression parse on certain tags.
          args:
              style (list): .
          returns:
              list