| add_heatmap_track | add heatmap to a new track |
| add_ideogram_track | Add ideogram track |
| add_lines_track | add lines to a new or exsited track |
| add_points_track | add points to a new or exsited track |
| add_rect_track | add retangles to a new or exsited track |
| add_segments_track | add segments to a new or exsited track |
| add_track | Add self-defined graphics track by track |
| current_track | The index of current track |
| get_cell_meta_data | Get meta data in a cell |
| gtrellis_layout | Initialize genome-level Trellis layout |
| gtrellis_show_index | Show index on each cell |