Expands all fold triggers.

def expand_all(self):
        """Expands all fold triggers."""
        block = self.editor.document().firstBlock()
        while block.isValid():
            TextBlockHelper.set_collapsed(block, False)
            block.setVisible(True)
            block = block.next()
        self._clear_block_deco()
        self._refresh_editor_and_scrollbars()
        self.expand_all_triggered.emit()