I guess that what you wanna do is use a button to trigger the report download. If that is your case you could do it like:

def get_label(self, cr, uid, ids, context=None):
    if ids:
       if not isinstance(ids, list):
           ids = [ids]
       context = dict(context or {}, active_ids=ids, active_model=self._name)
   return {
      'type': 'ir.actions.report.xml',
      'report_name': 'mrp.product_label_document',
      'context': context,
   }