docs: def poify(self, model):
          """turn a django model into a po file."""
          if not hasattr(model, 'localized_fields'):
              return None
  
          # create po stream with header
          po_stream = polibext.PoStream(StringIO.StringIO(self.po_header)).parse()
  
          for (name, field) in easymode.tree.introspection.get_default_field_descriptors(model):
              occurrence = u"%s.%s.%s" % (model._meta.app_label, model.__class__.__name__, name)
              value = field.value_to_string(model)
  
              # only add empty strings
              if value != "":
                  entry = polib.POEntry(msgid=value, occurrences=[(occurrence, model.pk)])
                  # make sure no duplicate entries in the po_stream
                  existing_entry = po_stream.find(entry.msgid)
                  if existing_entry is None:
                      po_stream.append(entry)
                  else:
                      # no really, existing_entry.merge does not merge the occurrences.
                      existing_entry.occurrences += entry.occurrences
  
          return po_stream