code: public static MemorySize getJobManagerHeapMemory(Configuration configuration) {
  		if (configuration.containsKey(JobManagerOptions.JOB_MANAGER_HEAP_MEMORY.key())) {
  			return MemorySize.parse(configuration.getString(JobManagerOptions.JOB_MANAGER_HEAP_MEMORY));
  		} else if (configuration.containsKey(JobManagerOptions.JOB_MANAGER_HEAP_MEMORY_MB.key())) {
  			return MemorySize.parse(configuration.getInteger(JobManagerOptions.JOB_MANAGER_HEAP_MEMORY_MB) + "m");
  		} else {
  			//use default value
  			return MemorySize.parse(configuration.getString(JobManagerOptions.JOB_MANAGER_HEAP_MEMORY));
  		}
  	}
docs: Get job manager's heap memory. This method will check the new key
  {@link JobManagerOptions#JOB_MANAGER_HEAP_MEMORY} and
  the old key {@link JobManagerOptions#JOB_MANAGER_HEAP_MEMORY_MB} for backwards compatibility.
  
  @param configuration the configuration object
  @return the memory size of job manager's heap memory.