Function create_fastcover_raw_dict_from_source 

pub fn create_fastcover_raw_dict_from_source<R: Read, W: Write>(
    source: R,
    output: &mut W,
    dict_size: usize,
    options: &FastCoverOptions,
) -> Result<FastCoverTuned>

Available on crate feature dict_builder only.

Train a raw FastCOVER dictionary from a source stream.

This function fully buffers the entire training corpus into memory via read_to_end, which can consume significant RAM for large inputs.