def mimetype_to_fmt(mimetype: str) ->str:
    """Get a format string given a mimetype."""
    if mimetype.startswith('application/vnd.vegalite'):
        return 'vega-lite'
    elif mimetype.startswith('application/vnd.vega'):
        return 'vega'
    elif mimetype == 'application/json':
        return 'json'
    elif mimetype == 'application/pdf':
        return 'pdf'
    elif mimetype == 'text/html':
        return 'html'
    elif mimetype == 'image/png':
        return 'png'
    elif mimetype == 'image/svg+xml':
        return 'svg'
    else:
        raise ValueError(f'Unrecognized mimetype={mimetype!r}')
