<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def item_selection_changed(self):
 """List widget item selection change handler."""

        row = self.current_row()
        if self.count() and row >= 0:
            if '</b></big><br>' in self.list.currentItem().text() and row == 0:
                self.next_row()
            if self.mode == self.FILE_MODE:
                try:
                    stack_index = self.paths.index(self.filtered_path[row])
                    self.plugin = self.widgets[stack_index][1]
                    self.goto_line(self.line_number)
                    try:
                        self.plugin.switch_to_plugin()
                        self.raise_()
                    except AttributeError:
                        # The widget using the fileswitcher is not a plugin
                        pass
                    self.edit.setFocus()
                except ValueError:
                    pass
            else:
                line_number = self.filtered_symbol_lines[row]
                self.goto_line(line_number)