def column_is_foreign_key(column):
    """Returns whether a column object is marked as a foreign key."""
    foreign_key = column["is foreign key"]
    if isinstance(foreign_key, str):
        foreign_key = foreign_key.lower()

        if foreign_key in {"y", "n", "yes", "no", "-"}:
            foreign_key = foreign_key in {"y", "yes"}
        else:
            raise ValueError(
                "Foreign key should be a boolean: "
                + foreign_key
                + ". Context: "
                + str(column)
            )

    return foreign_key