code: public IAtomType[] getAtomTypes(String symbol) {
          logger.debug("Request for atomtype for symbol ", symbol);
          List<IAtomType> atomList = new ArrayList<IAtomType>();
          for (IAtomType atomType : atomTypes.values()) {
              if (Objects.equals(atomType.getSymbol(), symbol)) {
                  atomList.add(atomType);
              }
          }
          IAtomType[] atomTypes = (IAtomType[]) atomList.toArray(new IAtomType[atomList.size()]);
          if (atomTypes.length > 0)
              logger.debug("Atomtype for symbol ", symbol, " has this number of types: " + atomTypes.length);
          else
              logger.debug("No atomtype for symbol ", symbol);
          return atomTypes;
      }
docs: Get an array of all atomTypes known to the AtomTypeFactory for the given
  element symbol and atomtype class.
  
  @param  symbol  An element symbol to search for
  @return         An array of atomtypes that matches the given element symbol
  and atomtype class