code: public void placeHydrogens2D(IAtomContainer container, IAtom atom) {
          double bondLength = GeometryUtil.getBondLengthAverage(container);
          placeHydrogens2D(container, atom, bondLength);
      }
docs: Place hydrogens connected to the given atom using the average bond length
  in the container.
  
  @param container atom container of which <i>atom</i> is a member
  @param atom      the atom of which to place connected hydrogens
  @throws IllegalArgumentException if the <i>atom</i> does not have 2d
  coordinates
  @see #placeHydrogens2D(org.openscience.cdk.interfaces.IAtomContainer,
  double)