code: def _find_proj_root():
      # type: () -> Optional[str]
      
      proj_files = frozenset(('pelconf.py', 'pelconf.yaml'))
      curr = os.getcwd()
  
      while curr.startswith('/') and len(curr) > 1:
          if proj_files & frozenset(os.listdir(curr)):
              return curr
          else:
              curr = os.path.dirname(curr)
  
      return None
docs: Find the project path by going up the file tree.
  
      This will look in the current directory and upwards for the pelconf file
      (.yaml or .py)