code: @Override
      public boolean setReactantCoefficient(IAtomContainer reactant, Double coefficient) {
          boolean result = reactants.setMultiplier(reactant, coefficient);
          return result;
      }
docs: Sets the coefficient of a a reactant to a given value.
  
  @param   reactant    Reactant for which the coefficient is set
  @param   coefficient The new coefficient for the given reactant
  @return  true if Molecule has been found and stoichiometry has been set.
  @see     #getReactantCoefficient