code: @Override
      public void addAtom(IAtom atom) {
          if (contains(atom)) {
              return;
          }
  
          if (atomCount + 1 >= atoms.length) {
              growAtomArray();
          }
          atom.addListener(this);
          atoms[atomCount] = atom;
          atomCount++;
          notifyChanged();
      }
docs: Adds an atom to this container.
  
  @param  atom  The atom to be added to this container