code: def personByEmailAddress(self, address):
          
          email = self.store.findUnique(EmailAddress,
                                        EmailAddress.address == address,
                                        default=None)
          if email is not None:
              return email.person
docs: Retrieve the L{Person} item for the given email address
          (or return None if no such person exists)
  
          @type name: C{unicode}