public VersionDefinitionXml getVersionDefinition(String versionDefinitionId) {
    ensureVersionDefinitions();

    return versionDefinitions.get(versionDefinitionId);
  }
@param versionDefinitionId the version definition id
@return the definition, or {@code null} if not found
ambari-server/src/main/java/org/apache/ambari/server/api/services/AmbariMetaInfo.java