code: public static FunctionMapper newFunctionMapper() {
          ServiceLoader<FunctionMapperSpi> loader = loadFunctionMapperSpi();
  
          // load FunctionMapperSpi instances
          ConcurrentMap<String, FunctionMapperSpi> functionMappers = new ConcurrentHashMap<>();
          for (FunctionMapperSpi functionMapperSpi : loader) {
              String prefixName = functionMapperSpi.getPrefixName();
              FunctionMapperSpi oldFunctionMapperSpi = functionMappers.putIfAbsent(prefixName, functionMapperSpi);
              if (oldFunctionMapperSpi != null) {
                  throw new ELException(String.format("Duplicate prefix function mapper: %s", prefixName));
              }
          }
  
          return new FunctionMapper(functionMappers);
      }
docs: Creates a new Function Mapper.
  @return returns an instance of the FunctionMapper