code: function(name, fn) {
      const externalName = this.store.toExternalAttributeName(name)
      this.instanceMethods.__defineSetter__(name, fn)
      if(externalName !== name) this.instanceMethods.__defineSetter__(externalName, fn)
      return this
    }
docs: Add a custom setter to your record
  
  @class Definition
  @method setter
  @param {string} name - The setter name
  @param {function} fn - The method to call
  
  @return {Definition}