rows = set()
for index in indexes:
  if index.isValid():
    rows.add(index.row)

for row in rows:
  // write row to stream

def mimeData(self, indexes):
        mimeData=QtCore.QMimeData()
        encodedData=QtCore.QByteArray()

        stream=QtCore.QDataStream(encodedData, QtCore.QIODevice.WriteOnly)
        for index in indexes:
            if index.isValid():
                text=self.data(index, QtCore.Qt.DisplayRole)
                stream.writeQVariant(text)
        mimeData.setData("application/draganddropdata.text.list", encodedData)
        return mimeData

def dropMimeData(self, data, action, row, column, parent):
        if action == QtCore.Qt.IgnoreAction:
            return True
        if not data.hasFormat("application/draganddropdata.text.list"):
            return False

        encodedData = data.data("application/draganddropdata.text.list")
        stream = QtCore.QDataStream(encodedData, QtCore.QIODevice.ReadOnly)

        items = []
        while not stream.atEnd():
            text = stream.readQVariant().toString().toUtf8()
            items.append(str(text))
        if len(items) > 0:
            self.emit(QtCore.SIGNAL('treeDropData'), items)

        return True