def add_sinks(sinks, sinks_to_add, ignore_index=True):
    """
    Add new sinks to the dataframe *sinks*.

    Parameters
    ----------
    sinks: DataFrame
        Dataframe of the sinks.
    sinks_to_add: DataFrame
        Dataframe of the sinks to add.
    ignore_index: bool, optional
        If True, reset the indices to integers, else use the indices provided.
        Default is True.

    Returns
    -------
    DataFrame
        Appended dataframe of the sinks.
    """
    sinks_ = sinks.append(sinks_to_add, ignore_index=ignore_index)
    return sinks_
