fn visit_map()

in tokenizers/src/models/bpe/serialization.rs [78:155]
77 lines of code
10 McCabe index (conditional complexity)

    fn visit_map<V>(self, mut map: V) -> std::result::Result<Self::Value, V::Error>
    where
        V: MapAccess<'de>,
    {
        let mut builder = BpeBuilder::new();
        let mut vocab: Option<AHashMap<String, u32>> = None;

        #[derive(Debug, Deserialize)]
        #[serde(untagged)]
        enum MergeType {
            Tuple(Vec<(String, String)>),
            Legacy(Vec<String>),
        }
        let mut merges: Option<MergeType> = None;
        while let Some(key) = map.next_key::<String>()? {
            match key.as_ref() {
                "dropout" => {
                    if let Some(dropout) = map.next_value()? {
                        builder = builder.dropout(dropout);
                    }
                }
                "unk_token" => {
                    if let Some(unk) = map.next_value()? {
                        builder = builder.unk_token(unk);
                    }
                }
                "continuing_subword_prefix" => {
                    if let Some(prefix) = map.next_value()? {
                        builder = builder.continuing_subword_prefix(prefix);
                    }
                }
                "end_of_word_suffix" => {
                    if let Some(suffix) = map.next_value()? {
                        builder = builder.end_of_word_suffix(suffix);
                    }
                }
                "fuse_unk" => {
                    if let Some(suffix) = map.next_value()? {
                        builder = builder.fuse_unk(suffix);
                    }
                }
                "byte_fallback" => {
                    if let Some(suffix) = map.next_value()? {
                        builder = builder.byte_fallback(suffix);
                    }
                }
                "ignore_merges" => {
                    if let Some(suffix) = map.next_value()? {
                        builder = builder.ignore_merges(suffix);
                    }
                }
                "vocab" => vocab = Some(map.next_value()?),
                "merges" => merges = Some(map.next_value()?),
                "type" => match map.next_value()? {
                    "BPE" => {}
                    u => {
                        return Err(serde::de::Error::invalid_value(
                            serde::de::Unexpected::Str(u),
                            &"BPE",
                        ))
                    }
                },
                _ => {}
            }
        }
        if let (Some(vocab), Some(merges)) = (vocab, merges) {
            let merges = match merges {
                MergeType::Tuple(merges) => merges,
                MergeType::Legacy(merges) => {
                    convert_merges_to_hashmap(merges.into_iter(), &vocab).map_err(Error::custom)?
                }
            };
            builder = builder.vocab_and_merges(vocab, merges);
            Ok(builder.build().map_err(Error::custom)?)
        } else {
            Err(Error::custom("Missing vocab/merges"))
        }
    }