read_drugbank_xml_db loads DrugBank xml database full tree
into memory.
read_drugbank_xml_db(db_path)loaded DB or NULL
string, full path for the DrugBank xml or zip file.
This functions reads DrugBank xml database and load it into memory for later processing. Hence; this method must be called before any other function in the package and it needs to be called one time only.
It takes one single mandatory argument which is the location of DrugBank db.