docs: def checksum_file(scheme, path):
      """Return the checksum (hex digest) of a file"""
      h = getattr(hashlib, scheme)()
  
      with open(path, 'rb') as f:
          chunk = f.read(65535)
          while chunk:
              h.update(chunk)
              chunk = f.read(65535)
      return h.hexdigest()