code: public static List<CDKRMap> getIsomorphMap(IAtomContainer sourceGraph, IAtomContainer targetGraph,
              boolean shouldMatchBonds) throws CDKException {
          if (sourceGraph instanceof IQueryAtomContainer) {
              throw new CDKException("The first IAtomContainer must not be an IQueryAtomContainer");
          }
  
          List<CDKRMap> result = null;
  
          List<List<CDKRMap>> rMapsList = search(sourceGraph, targetGraph, getBitSet(sourceGraph),
                  getBitSet(targetGraph), false, false, shouldMatchBonds);
  
          if (!rMapsList.isEmpty()) {
              result = rMapsList.get(0);
          }
  
          return result;
      }
docs: Returns the first isomorph mapping found or null.
  
  @param  sourceGraph  first molecule. Must not be an IQueryAtomContainer.
  @param  targetGraph  second molecule. May be an IQueryAtomContainer.
  @param shouldMatchBonds
  @return     the first isomorph mapping found projected of sourceGraph. This is atom List of CDKRMap objects containing Ids of matching bonds.
  @throws CDKException