code: public static Long getProcessInstanceId(Command<?> command) {
  		if (command instanceof ProcessInstanceIdCommand) {
  			return ((ProcessInstanceIdCommand) command).getProcessInstanceId();
  		} 
  
          return null;
  		
  	}
docs: Returns the process instance id field in a command, if available
  </p>
  See the CommonUtils.testProcessInstanceIdCommands test in this module
  
  @param command The {@link Command} instance
  @return the process instance id, if it's available in this command