def to_spark(self, index_col: Optional[Union[(str, List[str])]]=None) -> SparkDataFrame:
    if (index_col is None):
        log_advice('If `index_col` is not specified for `to_spark`, the existing index is lost when converting to Spark DataFrame.')
    return self._to_spark(index_col)
def to_spark(self, index_col: Optional[Union[(str, List[str])]]=None) -> SparkDataFrame:
    if (index_col is None):
        log_advice('If `index_col` is not specified for `to_spark`, the existing index is lost when converting to Spark DataFrame.')
    return self._to_spark(index_col)