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how to use

```rust fn main() { #[derive(Deserialize)] struct Foo { #[serde(deserializewith = "stringtrim")] name: String, } let json = r#"{"name":" "}"#; let foo = serdejson::fromstr::(json).unwrap(); assert_eq!(foo.name, "");

#[derive(Deserialize)]
struct OptionFoo {
    #[serde(deserialize_with = "option_string_trim")]
    name: Option<String>,
}
let json = r#"{"name":" "}"#;
let foo = serde_json::from_str::<OptionFoo>(json).unwrap();
assert_eq!(foo.name, None);

} ```