def freeze(h, output_yaml, resolve, groups):
    """Output installed packages."""
    if not groups:
        groups = filter(lambda group: not group.lower().startswith("bower"),
                        h.requirements.keys())
    else:
        groups = [text_type.strip(group) for group in groups.split(",")]

    if output_yaml:
        for requirements in h.requirements.values():
            for requirement in requirements:
                if resolve and not requirement.version:
                    requirement.load_installed_version()
        click.echo(h.requirements.yaml)
    else:
        for group in groups:
            if not h.requirements[group]:
                continue
            click.echo("# {}".format(group))
            for requirement in h.requirements[group]:
                if resolve and not requirement.version:
                    requirement.load_installed_version()
                click.echo(str(requirement))
def select_backend(self, backend_id=None):
        """
        Selects the backend corresponding to backend_id.
        If backend_id is none, refreshes the current configuration panel.

        @param backend_id: the id of the backend to select
        """
        selection = self.get_selection()
        if backend_id in self.backendid_to_iter:
            backend_iter = self.backendid_to_iter[backend_id]
            if selection:
                selection.select_iter(backend_iter)
        else:
            if self._get_selected_path():
                # We just reselect the currently selected entry
                self.on_select_row()
            else:
                # If nothing is selected, we select the first entry
                if selection:
                    selection.select_path("0")
        self.dialog.on_backend_selected(self.get_selected_backend_id())