| cett_nodes_options | returns carriers, enzymes,targets and transporters node valid options. |
| drug_node_options | returns drug node valid options. |
| parseDrugBank | parseDrugBank |
| references_node_options | returns references node valid options. |
| show_dvobject_metadata | init_dvobject Returns data.frame with two columns (key, value) of dvobject attributes |