def infer_type_from_keys(keys: list):
    """infer ddf data type from the primary key"""
    if len(keys) == 1:
        if keys[0] == 'concept':
            return 'concepts'
        else:
            return 'entities'
    if 'synonym' in keys:
        return 'synonyms'
    else:
        return 'datapoints'