Function from_the_open 

pub fn from_the_open(
    left_out: &[(FileFormat, usize)],
    lake: Option<&str>,
    files_differ: Disagreement,
    names_look_like_data: bool,
) -> Vec<Note>

What the open has to say before any footer: which data files this read passed over, and whether a lake table is read as its plain files. Choices, not defects: datui never refuses a read asked for, and says what it did instead.