@Override
  public Map getAll(Collection keys, Object aCallbackArgument) {
    if (keys == null) {
      throw new NullPointerException("The collection of keys for getAll cannot be null");
    }
    checkReadiness();
    checkForLimitedOrNoAccess();
    return keys.isEmpty() ? new HashMap() : basicGetAll(keys, aCallbackArgument);
  }
@param key the key to find
@param aCallbackArgument argument for callbacks
@param generateCallbacks whether callbacks should be invoked
@param clientEvent client-side event, if any (used to pass back version information)
@return the value associated with the key
geode-core/src/main/java/org/apache/geode/internal/cache/AbstractRegion.java