in src/edwards.rs [245:272]
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
        where D: Deserializer<'de>
    {
        struct EdwardsPointVisitor;
        impl<'de> Visitor<'de> for EdwardsPointVisitor {
            type Value = EdwardsPoint;
            fn expecting(&self, formatter: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
                formatter.write_str("a valid point in Edwards y + sign format")
            }
            fn visit_seq<A>(self, mut seq: A) -> Result<EdwardsPoint, A::Error>
                where A: serde::de::SeqAccess<'de>
            {
                let mut bytes = [0u8; 32];
                for i in 0..32 {
                    bytes[i] = seq.next_element()?
                        .ok_or(serde::de::Error::invalid_length(i, &"expected 32 bytes"))?;
                }
                CompressedEdwardsY(bytes)
                    .decompress()
                    .ok_or(serde::de::Error::custom("decompression failed"))
            }
        }
        deserializer.deserialize_tuple(32, EdwardsPointVisitor)
    }