def METHOD_NAME(base_node, seq):
    if 'children' not in base_node:
        base_node['children'] = []
    mutations = get_differences(base_node, seq)
    new_node = get_node_struct(seq)
    new_node['branch_attrs']['mutations']['nuc'] = mutations
    new_node['node_attrs']['div'] = base_node['node_attrs']['div'] + len(mutations)
    new_node['mutations'] = deepcopy(base_node['mutations'])
    for mut in mutations:
        anc, pos, der = mut[0], int(mut[1:-1])-1, mut[-1]
        new_node['mutations'][pos] = der
    base_node['children'].append(new_node)