A string indicating the study ID from which to pull data. If no study ID, will
guess the study ID based on your URL and inform. Only 1 study ID can be passed. If mutations/cna from
more than 1 study needed, see sample_study_pairs
patient_id
a cBioPortal patient_id
clinical_attribute
one or more clinical attributes for your study.
If none provided, will return all attributes available for studies
base_url
The database URL to query
If NULL will default to URL set with set_cbioportal_db(<your_db>)