import re


def get_nom_val(atrv):
    """Given a string containing a nominal type, returns a tuple of the
    possible values.

    A nominal type is defined as something framed between braces ({}).

    Parameters
    ----------
    atrv : str
       Nominal type definition

    Returns
    -------
    poss_vals : tuple
       possible values

    Examples
    --------
    >>> get_nom_val("{floup, bouga, fl, ratata}")
    ('floup', 'bouga', 'fl', 'ratata')
    """
    r_nominal = re.compile('{(.+)}')
    m = r_nominal.match(atrv)
    if m:
        return tuple(i.strip() for i in m.group(1).split(','))
    else:
        raise ValueError("This does not look like a nominal string")