docs: def createContactItem(self, person, label, number):
          """
          Create a L{PhoneNumber} item for C{number}, associated with C{person}.
  
          @type person: L{Person}
  
          @param label: The value to use for the I{label} attribute of the new
          L{PhoneNumber} item.
          @type label: C{unicode}
  
          @param number: The value to use for the I{number} attribute of the new
          L{PhoneNumber} item.  If C{''}, no item will be created.
          @type number: C{unicode}
  
          @rtype: L{PhoneNumber} or C{NoneType}
          """
          if number:
              return PhoneNumber(
                  store=person.store, person=person, label=label, number=number)