def remove(self, elem):
        """Remove a requirement.

        :param elem: a string or :class:`Requirement` instance.
        """
        if isinstance(elem, text_type):
            for requirement in self:
                if requirement.package == elem:
                    return super(Requirements, self).remove(requirement)
        return super(Requirements, self).remove(elem)
def on_select_row(self, treeview=None):
        """When a row is selected, displays the corresponding editing panel

        @var treeview: not used
        """
        self.dialog.on_backend_selected(self.get_selected_backend_id())