code: function initGlobal (args) {
      // do nothing if global data already defined
      if (global.__immutable_core_model__) {
          return
      }
      // create new global object
      var GLOBAL = global.__immutable_core_model__ = {
          // number of concurrent related queries to allow per query
          concurrency: 5,
          // default to use binary columns for ids
          defaultBinaryIds: true,
          // default character set
          defaultCharset: 'utf8',
          // default compression setting
          defaultCompression: true,
          // default elastic search client
          defaultElasticsearch: undefined,
          // default database engine
          defaultEngine: 'InnoDB',
          // default insert delayed option for myisam tables
          defaultInsertDelayed: false,
          // map of models indexed by name
          models: {},
      }
      // create validator as global object so that schemas will be shared
      // between all model classes
      GLOBAL.validator = new Ajv({
          allErrors: true,
          coerceTypes: 'array',
          removeAdditional: true,
          useDefaults: true,
          v5: true,
      })
  }
docs: @function initGlobal
  
  initialize global data