proc `$`(df: DataFrame): string {....raises: [ValueError, Exception],
                                  tags: [ReadEnvEffect, RootEffect], forbids: [].}

proc `[]`(df: DataFrame; colIdx: int): Vector {....raises: [], tags: [],
    forbids: [].}

proc `[]`(df: DataFrame; colName: string): Vector {....raises: [ValueError],
    tags: [], forbids: [].}

proc columnNames(df: DataFrame): seq[string] {....raises: [], tags: [], forbids: [].}

proc len(df: DataFrame): int {....raises: [], tags: [], forbids: [].}

proc newDataFrame(data: OrderedTable[string, Vector]): DataFrame {.
    ...raises: [ValueError], tags: [], forbids: [].}

iterator rows(df: DataFrame): seq[Value] {....raises: [ValueError], tags: [],
    forbids: [].}