code: def _make_suffix(cov):
      
      # Check if coverage object has data_suffix:
      if cov and cov.data_suffix is not None:
          # If True, the suffix will be autogenerated by coverage.py.
          # The suffixed data files will be automatically combined later.
          if cov.data_suffix is True:
              return True
          # Has a suffix, but we add our own extension
          return cov.data_suffix + '.nbval'
      return 'nbval'
docs: Create a suffix for nbval data file depending on pytest-cov config.