def load_parameters():
    descendant_dict = defaultdict()
    with open(input_file, 'r') as f:
        all_lines = f.readlines()
        aln_file = all_lines[0].strip()
        if not os.path.exists(aln_file):
            logger.error('Invalid cDNA alignment file: {0}'.format(aln_file))
            sys.exit(1)
        logger.info('Input cDNA alignment file: {0}'.format(aln_file))
        seq_id_dict = defaultdict()
        seq_id_list = []
        for seq_record in AlignIO.read(aln_file, 'fasta'):
            seq_id_dict[str(seq_record.id)] = 1
            seq_id_list.append(str(seq_record.id))
        tree_file = all_lines[1].strip()
        if not os.path.exists(tree_file):
            logger.error('Invalid tree file: {0}'.format(tree_file))
            sys.exit(1)
        logger.info('Input tree file: {0}'.format(tree_file))
        tmp_t = Tree(tree_file, format=0)
        node_id_dict = defaultdict()
        for node in tmp_t:
            node_id_dict[str(node.name)] = 1
        if seq_id_dict != node_id_dict:
            if len(seq_id_dict) < len(node_id_dict):
                logger.warning('Sequences is less than tree nodes.')
                logger.info('Trim input tree file.')
                tree_file = trim_tree(tree_file, seq_id_list)
            else:
                logger.error('Sequences is falsely greater than tree nodes.')
                sys.exit(1)
        t = EvolTree(tree_file, format=1)
        for descendant in t.iter_descendants():
            descendant_dict[descendant.node_id] = str(descendant)
        root = t.get_tree_root()
        id_list = []
        for leaf in t.traverse('preorder'):
            id_list.append(leaf.node_id)
        select_nodes = []
        if len(all_lines) > 2:
            for each_line in all_lines[2:]:
                s = each_line.strip()
                if s:
                    select_nodes.append(s)
        if select_nodes:
            nodes_line = ', '.join(select_nodes)
            logger.info('Input nodes: {0}'.format(nodes_line))
            for node in select_nodes:
                if node not in t:
                    logger.error('Error node: {0}'.format(node))
                    sys.exit(1)
            if not t.check_monophyly(values=select_nodes, target_attr='name'):
                logger.error('Some nodes are not monophyletic.')
                sys.exit(1)
            common_ancestor = t.get_common_ancestor(select_nodes)
        else:
            common_ancestor = root
            logger.info('No specific node')
        run_list = []
        for s in common_ancestor.iter_descendants():
            run_list.append(s.node_id)
        logger.info('These node ids will be checked: {0}'.format(
            str(run_list)))
        return run_list, aln_file, tree_file, descendant_dict