List children terms of current taxonomy term

wp_list_children_terms.php

<?php
	$queried_object = get_queried_object();
	$taxonomy = $queried_object->taxonomy;
	$term_id = $queried_object->term_id;
	$taxonomy_name = 'category';
	$term_children = get_term_children($term_id, $taxonomy_name);

	echo '<ul class="nav nav-pills">';
		foreach ($term_children as $child) {
			$term = get_term_by('id', $child, $taxonomy_name);
			echo '<li><a class="btn btn-default" href="' . get_term_link($child, $taxonomy_name) . '">' . $term->name . '</a></li>';
		}
	echo '</ul>';
?>