Define the API of a standard editing widget.
EditWidgetABC subclasses support a specific set of types, defined by thier types class method. They may also handle and return None, which usually indicates an invalid value. It is up to the subclass implementation to deal with type checking and conversions.
The metaclass inherits from the following. EditWidgetABC itself only inherits from object.
Return the value of the widget. This is similar to PySide.QtGui.QLineEdit.text.
Set the value of the widget. This is similar to PySide.QtGui.QLineEdit.setText.
Called by subclasses to raise the valueChanged signal.