def METHOD_NAME(self, key, *, fout=None):
    """
    Display a single catalog of given key.
    If not found, nothing is written out.
    Parameters
    ----------
    key : str
        Catalog key.
    fout : output stream
        Default is screen output.
    """
    if fout is None:  # pragma: no cover
        fout = sys.stdout
    str_list = []
    for typ in self.dbtypes:
        if key in self.catkeys[typ]:
            str_list += [self.dbs[typ].get_catalog(key).dumps(),
                         '\nFound in {0}'.format(typ)]
            # Only has one match, so quits when it is found
            break
    if len(str_list) > 0:
        fout.write('\n'.join(str_list) + '\n')