code: function checkDefined(key) {
              //noinspection JSPotentiallyInvalidUsageOfThis
              if (! data[`${this.moduleName}.${key}`] && typeof parent.get(key) !== 'undefined' && ! util.squelch()) {
                  // Not allowing sub-modules to name variables already defined in the parent (unless using override).
                  // Things get weird when expecting a variable defined in two places.
                  //noinspection JSPotentiallyInvalidUsageOfThis
                  util.throw(`In "${this.moduleName}" variable "${key}" defined in module "${parent.moduleName}". Choose a different name.`);
              }
          }
docs: Used to prevent users from overriding a key without using a function meant to explicitly do so.
  Only works when `window.DEV_MODE` is 'strict' or 'warn'
  @param {string} key