code: public boolean isModifiedOnVersion(String version) {
  		if (version == null || version.isEmpty()) {
  			return true;
  		}
  		for (ModificationRecord record : this.modificationRecordList) {
  			if (record.isModifiedOnVersion(version)) {
  				return true;
  			}
  		}
  		return false;
  	}
docs: /*
  @return Whether history contains modification on specified version. If no
  version specified, returns true.