def update_notes(notes)
      return false unless link? :notes
      self.attributes = notes
      reload follow_link(:notes, body: to_xml)
      true
    end
def update_notes(notes)
      return false unless link? :notes
      self.attributes = notes
      reload follow_link(:notes, body: to_xml)
      true
    end
Update the notes sections of the subscription. This endpoint also allows you to
 update the custom fields.

 @example
   subscription.custom_fields.first.value = nil
   subscription.update_notes(terms_and_conditions: 'New T&C')
   #=>
   #   <subscription>
   #     <custom_fields><custom_field><name>food</name><value nil="nil"/><custom_field></custom_fields>
   #     <terms_and_conditions>New T&C</terms_and_conditions>
   #   </subscription>
   # it's also okay to call without notes
   subscription.update_notes({})

 @param notes [Hash] should be the notes parameters you wish to update
 @return [true, false] +true+ when successful, +false+ when unable to