code: @Override
      public boolean matches(IAtom atom) {
          PharmacophoreAtom patom = PharmacophoreAtom.get(atom);
          return patom.getSymbol().equals(getSymbol());
      }
docs: Checks whether this query atom matches a target atom.
  
  Currently a query pharmacophore atom will match a target pharmacophore group if the
  symbols of the two groups match. This is based on the assumption that
  pharmacophore groups with the same symbol will have the same SMARTS
  pattern.
  
  @param atom A target pharmacophore group
  @return true if the current query group has the same symbol as the target group