Returns the first five rows of a table as JSON. Inlcudes all columns.
    Uses Pandas' "split" JSON format.

def table_preview(table_name):
    """
    Returns the first five rows of a table as JSON. Inlcudes all columns.
    Uses Pandas' "split" JSON format.

    """
    preview = orca.get_table(table_name).to_frame().head()
    return (
        preview.to_json(orient='split', date_format='iso'),
        200,
        {'Content-Type': 'application/json'})