Function serialize 

pub fn serialize<K, V, S>(
    data: &[(K, V)],
    serializer: S,
) -> Result<S::Ok, S::Error>
where
    S: Serializer,
    K: Serialize,
    V: Serialize,

Serialize an array of (K, V) pairs as if it were a HashMap<K, V>.

In formats where dictionaries are ordered, this maintains the input data’s order. Each pair is treated as a single entry into the dictionary.

Behavior when duplicate keys are present in the data is unspecified and serializer-dependent. This function does not check for duplicate keys and will not warn the serializer.