code: def _expand_targets(self, targets, base_dir=None):
          
          all_targets = []
  
          for target in targets:
              target_dirs = [p for p in [base_dir, os.path.dirname(target)] if p]
              target_dir = target_dirs and os.path.join(*target_dirs) or ''
              target = os.path.basename(target)
              target_path = os.path.join(target_dir, target)
  
              if os.path.exists(target_path):
                  all_targets.append(target_path)
  
                  with open(target_path) as fp:
                      for line in fp:
                          if line.startswith('-r '):
                              _, new_target = line.split(' ', 1)
                              all_targets.extend(self._expand_targets([new_target.strip()], base_dir=target_dir))
  
          return all_targets
docs: Expand targets by looking for '-r' in targets.