Update unconstrained.rs

crates/recursion/core/src/runtime/unconstrained.rs

@@ -1,5 +1,18 @@
+use super::io::StdinBuffer;
+
+pub struct UnconstrainedBlock {
+    pub stdin_buffer: StdinBuffer,
+    // other fields, if any...
+}
+
 impl UnconstrainedBlock {
-    // Adding a new method to write to the front of the queue
+    pub fn new() -> Self {
+        Self {
+            stdin_buffer: StdinBuffer::new(),
+            // initialization of other fields...
+        }
+    }
+
     pub fn write_front(&mut self, data: Vec<u8>) {
         self.stdin_buffer.write_front(data);
     }