Add code

example_10/.gitignore

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+/target

example_10/Cargo.toml

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+[package]
+name = "example_10"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+serde = { version = "1", features = ["derive"] }
+
+[features]
+default = ["test"]
+
+test = []

example_10/src/main.rs

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+use serde::Deserialize;
+use serde::Serialize;
+
+macro_rules! assert_eq {
+    ($left:expr, $right:expr) => {
+        let left = $left;
+        let right = $right;
+        if left != right {
+            panic!("assertion failed: {:?} != {:?}", left, right);
+        }
+    };
+}
+
+#[derive(Serialize, Deserialize)]
+struct Person {
+    name: String,
+    age: u32,
+}
+
+fn main() {
+    assert_eq!(1 + 1, 2);
+
+    if cfg!(feature = "test") {
+        println!("yes")
+    } else {
+        println!("no")
+    }
+}