Checks to see if the configuration file contains a SUPERNOVA_GROUP
    configuration option.

def is_valid_group(group_name, nova_creds):
    """
    Checks to see if the configuration file contains a SUPERNOVA_GROUP
    configuration option.
    """
    valid_groups = []
    for key, value in nova_creds.items():
        supernova_groups = value.get('SUPERNOVA_GROUP', [])
        if hasattr(supernova_groups, 'startswith'):
            supernova_groups = [supernova_groups]
        valid_groups.extend(supernova_groups)
    valid_groups.append('all')
    if group_name in valid_groups:
        return True
    else:
        return False