code: def store(self, database, validate=True, role=None):
          
          if validate:
              self.validate()
          self._id, self._rev = database.save(self.to_primitive(role=role))
          return self
docs: Store the document in the given database.
  
          :param database: the `Database` object source for storing the document.
          :return: an updated instance of `Document` / self.