Function deserialize_external_value 

pub fn deserialize_external_value<T, F>(
    raw: Value,
    label: &str,
    shape_error: F,
) -> Result<T, DagMlError>
where
    T: DeserializeOwned + Serialize,
    F: Fn(String) -> DagMlError,

Deserialize a public contract that has already crossed a structured host boundary (for example a Python mapping), while preserving the same object/array rules as deserialize_external_contract.