def METHOD_NAME(migrations_root: Text,
                            current_migration_number: Optional[int]
                           ) -> Sequence[Text]:
  """Lists filenames of migrations with numbers bigger than a given one."""
  migrations = []
  for m in os.listdir(migrations_root):
    if (current_migration_number is None or
        _MigrationFilenameToInt(m) > current_migration_number):
      migrations.append(m)
  return sorted(migrations, key=_MigrationFilenameToInt)