code: def _mint_new_study_id(self):
          
          # studies created by the OpenTree API start with ot_,
          # so they don't conflict with new study id's from other sources
          with self._doc_counter_lock:
              c = self._advance_new_study_id()
          # @TODO. This form of incrementing assumes that
          #   this codebase is the only service minting
          #   new study IDs!
          return "{p}{c:d}".format(p=self._new_study_prefix, c=c)
docs: Checks out master branch as a side effect