code: @Inline(value = "$1.putAll($2)", statementExpression = true)
  	public static <K, V> void operator_add(Map<K, V> outputMap, Map<? extends K, ? extends V> inputMap) {
  		outputMap.putAll(inputMap);
  	}
docs: Add the given entries of the input map into the output map.
  
  <p>
  If a key in the inputMap already exists in the outputMap, its value is
  replaced in the outputMap by the value from the inputMap.
  </p>
  
  @param <K> type of the map keys.
  @param <V> type of the map values.
  @param outputMap the map to update.
  @param inputMap the entries to add.
  @since 2.15