code: def get_isomorphisms(reference, lig):
      
      query = pybel.ob.CompileMoleculeQuery(reference.OBMol)
      mappr = pybel.ob.OBIsomorphismMapper.GetInstance(query)
      if all:
          isomorphs = pybel.ob.vvpairUIntUInt()
          mappr.MapAll(lig.OBMol, isomorphs)
      else:
          isomorphs = pybel.ob.vpairUIntUInt()
          mappr.MapFirst(lig.OBMol, isomorphs)
          isomorphs = [isomorphs]
      write_message("Number of isomorphisms: %i\n" % len(isomorphs), mtype='debug')
      # #@todo Check which isomorphism to take
      return isomorphs
docs: Get all isomorphisms of the ligand.