def repr(self, changed_widgets=None):
        """It is used to automatically represent the object to HTML format
        packs all the attributes, children and so on.

        Args:
            changed_widgets (dict): A dictionary containing a collection of tags that have to be updated.
                The tag that have to be updated is the key, and the value is its textual repr.
        """
        if changed_widgets is None:
            changed_widgets = {}
        local_changed_widgets = {}
        _innerHTML = self.innerHTML(local_changed_widgets)

        if self._ischanged() or ( len(local_changed_widgets) > 0 ):
            self._backup_repr = ''.join(('<', self.type, ' ', self._repr_attributes, '>', 
                                        _innerHTML, '</', self.type, '>'))
            #faster but unsupported before python3.6
            #self._backup_repr = f'<{self.type} {self._repr_attributes}>{_innerHTML}</{self.type}>'
        if self._ischanged():
            # if self changed, no matter about the children because will be updated the entire parent
            # and so local_changed_widgets is not merged
            changed_widgets[self] = self._backup_repr
            self._set_updated()
        else:
            changed_widgets.update(local_changed_widgets)
        return self._backup_repr
It is used to automatically represent the object to HTML format
        packs all the attributes, children and so on.

        Args:
            changed_widgets (dict): A dictionary containing a collection of tags that have to be updated.
                The tag that have to be updated is the key, and the value is its textual repr.