docs: def editContactItem(self, contact, email):
          """
          Change the email address of the given L{EmailAddress} to that specified
          by C{email}.
  
          @type email: C{unicode}
          @param email: The new value to use for the I{address} attribute of the
              L{EmailAddress}.
  
          @return: C{None}
          """
          address = self._existing(email)
          if address is not None and address is not contact:
              raise ValueError('There is already a person with that email '
                               'address (%s): ' % (address.person.name,))
          contact.address = email