code: public static Stereo getStereo(IAtom atom1, IAtom atom2, IAtom atom3, IAtom atom4) {
  
          // a normal is calculated for the base atoms (2, 3, 4) and compared to
          // the first atom. PLUS indicates ACW.
          TetrahedralSign sign = StereoTool.getHandedness(atom2, atom3, atom4, atom1);
  
          if (sign == TetrahedralSign.PLUS) {
              return Stereo.ANTI_CLOCKWISE;
          } else {
              return Stereo.CLOCKWISE;
          }
      }
docs: Take four atoms, and return Stereo.CLOCKWISE or Stereo.ANTI_CLOCKWISE.
  The first atom is the one pointing towards the observer.
  
  @param atom1 the atom pointing towards the observer
  @param atom2 the second atom (points away)
  @param atom3 the third atom (points away)
  @param atom4 the fourth atom (points away)
  @return clockwise or anticlockwise