code: public ExecutionConfig setExecutionConfig(ExecutionConfig config) {
  		ExecutionConfig prev = executionConfig;
  		this.executionConfig = config;
  		return prev;
  	}
docs: Replaces the existing {@link ExecutionConfig} (possibly {@code null}), with the provided one.
  @param config The new {@code configuration}.
  @return The old configuration, or {@code null} if none was specified.