def _get_middle(token):
    """Return float given a string possibly including 'S'.

    Parameters
    ----------
    token : str
        String representation of middle layer_ ints, floats symmetric
        e.g. '800', '800.0', '400S'

    Examples
    --------
    >>> _get_middle('800.0')
    800.0
    >>> _get_middle('400S')
    800.0

    Notes
    -----
    The symmetry flag 'S' indicates doubling the numeric value.

    """
    if 'S' in token:
        return 2 * float(token[:-1])
    else:
        return float(token)
