code: @Nonnull
    public EChange removeVariable (@Nullable final QName aName)
    {
      if (aName == null)
        return EChange.UNCHANGED;
      return m_aMap.removeObject (aName);
    }
docs: Remove the variable with the specified name.
  
  @param aName
  The name to be removed. May be <code>null</code>.
  @return {@link EChange}