docs: def _mode(self, s):
          """Check file mode format and parse into an int.
  
          :return: mode as integer
          """
          # Note: Output from git-fast-export slightly different to spec
          if s in [b'644', b'100644', b'0100644']:
              return 0o100644
          elif s in [b'755', b'100755', b'0100755']:
              return 0o100755
          elif s in [b'040000', b'0040000']:
              return 0o40000
          elif s in [b'120000', b'0120000']:
              return 0o120000
          elif s in [b'160000', b'0160000']:
              return 0o160000
          else:
              self.abort(errors.BadFormat, 'filemodify', 'mode', s)