code: def set_symbol(self, symbol):
          
          raise "Deprecated"
          self.symbol, self.bondtype, bondorder, self.equiv_class = \
                       BONDLOOKUP[symbol]
          if self.bondtype == 4:
              self.aromatic = 1
          else:
              self.aromatic = 0
docs: (symbol, bondorder) -> set the bondsymbol
          of the molecule