def get_dir_from_zipfile(zip_file, fallback=None):
    """Return the name of the root folder in a zip file.

    :param zip_file: a :class:`zipfile.ZipFile` instance.
    :param fallback: if `None`, the name of the zip file is used. This is
        returned if the zip file contains more than one top-level directory,
        or none at all.
    """
    fallback = fallback or zip_file.filename
    directories = [name for name in zip_file.namelist() if name.endswith("/")
                   and len(PurePath(name).parts) == 1]
    return fallback if len(directories) > 1 else directories[0]
def log_row(self, row_category: str, row: List[int]):
        """Logs a confusion matrix row.

        Args:
          row_category: Category to which the row belongs.
          row: List of integers specifying the values for the row.

        Raises:
          ValueError: If row_category is not in the list of categories set in
            set_categories or size of the row does not match the size of
            categories.
        """
        if row_category not in self._categories:
            raise ValueError('Invalid category: {} passed. Expected one of: {}'.\
              format(row_category, self._categories))

        if len(row) != len(self._categories):
            raise ValueError('Invalid row. Expected size: {} got: {}'.\
              format(len(self._categories), len(row)))

        self._matrix[self._categories.index(row_category)] = row