code: @Nonnull
    public static <KEYTYPE, VALUETYPE> String getImplodedMapped (final char cSepOuter,
                                                                 final char cSepInner,
                                                                 @Nullable final Map <? extends KEYTYPE, ? extends VALUETYPE> aElements,
                                                                 @Nonnull final Function <? super KEYTYPE, String> aKeyMapper,
                                                                 @Nonnull final Function <? super VALUETYPE, String> aValueMapper)
    {
      return getImplodedMapped (Character.toString (cSepOuter),
                                Character.toString (cSepInner),
                                aElements,
                                aKeyMapper,
                                aValueMapper);
    }
docs: Get a concatenated String from all elements of the passed map, separated by
  the specified separator chars.
  
  @param cSepOuter
  The separator to use for separating the map entries.
  @param cSepInner
  The separator to use for separating the key from the value.
  @param aElements
  The map to convert. May be <code>null</code> or empty.
  @param aKeyMapper
  The mapping function to convert from KEYTYPE to String. May not be
  <code>null</code>.
  @param aValueMapper
  The mapping function to convert from VALUETYPE to String. May not be
  <code>null</code>.
  @return The concatenated string.
  @param <KEYTYPE>
  Map key type
  @param <VALUETYPE>
  Map value type
  @since 8.5.6