code: function(name, fn, internal) {
      const externalName = this.store.toExternalAttributeName(name)
      this.instanceMethods.__defineGetter__(name, fn)
      if(externalName !== name) this.instanceMethods.__defineGetter__(externalName, fn)
      if (!internal) this.definedGetter[name] = fn
  
      return this
    }
docs: getter function
  
  @public
  @callback getterFN
  @return *
  @this Model
   
  Add a custom getter to your record
  
  @public
  @memberof Definition
  @method getter
  @param {string} name - The getter name
  @param {getterFN} fn - The method to call
  
  @return {Definition}