code: public static int getSlot(Configuration configuration) {
  		int slots = configuration.getInteger(TaskManagerOptions.NUM_TASK_SLOTS, 1);
  		// we need this because many configs have been written with a "-1" entry
  		if (slots == -1) {
  			slots = 1;
  		}
  
  		ConfigurationParserUtils.checkConfigParameter(slots >= 1, slots, TaskManagerOptions.NUM_TASK_SLOTS.key(),
  			"Number of task slots must be at least one.");
  
  		return slots;
  	}
docs: Parses the configuration to get the number of slots and validates the value.
  
  @param configuration configuration object
  @return the number of slots in task manager