code: @Nonnull
    public EChange addAllFrom (@Nonnull final MapBasedXPathFunctionResolver aOther, final boolean bOverwrite)
    {
      ValueEnforcer.notNull (aOther, "Other");
      EChange eChange = EChange.UNCHANGED;
      for (final Map.Entry <XPathFunctionKey, XPathFunction> aEntry : aOther.m_aMap.entrySet ())
        if (bOverwrite || !m_aMap.containsKey (aEntry.getKey ()))
        {
          m_aMap.put (aEntry.getKey (), aEntry.getValue ());
          eChange = EChange.CHANGED;
        }
      return eChange;
    }
docs: Add all functions from the other function resolver into this resolver.
  
  @param aOther
  The function resolver to import the functions from. May not be
  <code>null</code>.
  @param bOverwrite
  if <code>true</code> existing functions will be overwritten with the
  new functions, otherwise the old functions are kept.
  @return {@link EChange}