Creates a new editor for the system.

def createEditor(self, parent, column, operator, value):
        """
        Creates a new editor for the system.
        """
        editor = super(EnumPlugin, self).createEditor(parent,
                                                      column,
                                                      operator,
                                                      value)
        
        editor.setEnum(column.enum())
        if operator in ('contains', 'does not contain'):
            editor.setCheckable(True)
        
        editor.setCurrentValue(value)
        return editor