When using QStandardItemModel and a QListView with a user defined drag and drop
mime-type, you get the following traceback:

python.exe main.py
Traceback (most recent call last):
  File "main.py", line 23, in mimeData
    self.__mimedata.setData(u'application/my-form',self.__qextra)
RuntimeError: Internal C++ object (PySide.QtCore.QMimeData) already deleted.
Traceback (most recent call last):
  File "main.py", line 23, in mimeData
    self.__mimedata.setData(u'application/my-form',self.__qextra)
RuntimeError: Internal C++ object (PySide.QtCore.QMimeData) already deleted.

Attached is an application that demonstrates the problem in PySide. It works
well if you run it in PyQt4. 

The application defines a mime type called 'application/my-form' in the
QListView's QStandardItemModel (MyItemModel) and list the content from the drop
in QTextEdit (MyTextEdit) using the defined mime-type.