@Override
  public void execute(FunctionContext context) {
    RegionFunctionContext regionContext = (RegionFunctionContext) context;
    Region dataSet = regionContext.getDataSet();
    Object key = regionContext.getFilter().iterator().next();
    Object value = regionContext.getArguments();
    dataSet.put(key, value);
    context.getResultSender().lastResult(Boolean.TRUE);
  }
Function that puts the value from the argument at the key passed in through the filter.
geode-assembly/geode-assembly-test/src/main/java/org/apache/geode/rest/internal/web/controllers/PutKeyFunction.java