Function deserialize_optional_decimal 

pub fn deserialize_optional_decimal<'de, D>(
    deserializer: D,
) -> Result<Option<Decimal>, <D as Deserializer<'de>>::Error>
where
    D: Deserializer<'de>,

Deserializes an optional Decimal from a string field.

Returns None if the string is empty or “0”, otherwise parses to Decimal.

Errors

Returns an error if the string cannot be parsed as a valid decimal.