Allow batch query for block hash. (#4210)

substrate/primitives/rpc/src/lib.rs

@@ -19,3 +19,20 @@
 #![warn(missing_docs)]
 
 pub mod number;
+pub mod list;
+
+/// A util function to assert the result of serialization and deserialization is the same.
+#[cfg(test)]
+pub(crate) fn assert_deser<T>(s: &str, expected: T) where
+	T: std::fmt::Debug + serde::ser::Serialize + serde::de::DeserializeOwned + PartialEq
+{
+	assert_eq!(
+		serde_json::from_str::<T>(s).unwrap(),
+		expected
+	);
+	assert_eq!(
+		serde_json::to_string(&expected).unwrap(),
+		s
+	);
+}
+