import asyncio

class Sandbox:
    def __init__(self):
        self._process = None
    async def start(self):
        if self._process is not None:
            raise ValueError("The sandbox has started")
        self._process = await asyncio.create_subprocess_exec(
                "sandbox",
                stdin = asyncio.subprocess.PIPE,
                stdout = asyncio.subprocess.PIPE)
    async def close(self):
        if self._process is None:
            raise ValueError("The sandbox has not started")
        if self._process.returncode is not None:
            return
        self._process.stdin.close()
        await self._process.wait()

    async def __aenter__(self):
        await self.start()
        return self
    async def __aexit__(self, exc_type, exc, tb):
        await self.close()

    async def execute(self, *args, **kwargs):
        raise NotImplementedError()
    async def read(self, filename):
        raise NotImplementedError()
    async def write(self, *args, **kwargs):
        raise NotImplementedError()

import asyncio

class Sandbox:
    def __init__(self):
        self._process = None
    async def start(self):
        if self._process is not None:
            raise ValueError("The sandbox has started")
        self._process = await asyncio.create_subprocess_exec(
                "sandbox",
                stdin = asyncio.subprocess.PIPE,
                stdout = asyncio.subprocess.PIPE)
    async def close(self):
        if self._process is None:
            raise ValueError("The sandbox has not started")
        if self._process.returncode is not None:
            return
        self._process.stdin.close()
        await self._process.wait()

    async def __aenter__(self):
        await self.start()
        return self
    async def __aexit__(self, exc_type, exc, tb):
        await self.close()

    async def execute(self, *args, **kwargs):
        raise NotImplementedError()
    async def read(self, filename):
        if b"\0" in filename:
            raise ValueError("filename contains null charactor")
        if b"\n" in filename:
            raise ValueError("filename contains newline")

        self._process.stdin.write(b"read %b\n" % filename)

        result = b"";
        while True:
            line = await self._process.stdout.readuntil()
            if line == b"ok\n":
                return result
            if line == b"error\n":
                raise asyncio.IncompleteReadError(result, None)
            count = int(line)
            result += await self._process.stdout.readexactly(count)

    async def write(self, *args, **kwargs):
        raise NotImplementedError()

Implement read of Python wrapper
Implement read of Python wrapper

  import asyncio
  
  class Sandbox:
      def __init__(self):
          self._process = None
      async def start(self):
          if self._process is not None:
              raise ValueError("The sandbox has started")
          self._process = await asyncio.create_subprocess_exec(
                  "sandbox",
                  stdin = asyncio.subprocess.PIPE,
                  stdout = asyncio.subprocess.PIPE)
      async def close(self):
          if self._process is None:
              raise ValueError("The sandbox has not started")
          if self._process.returncode is not None:
              return
          self._process.stdin.close()
          await self._process.wait()
  
      async def __aenter__(self):
          await self.start()
          return self
      async def __aexit__(self, exc_type, exc, tb):
          await self.close()
  
      async def execute(self, *args, **kwargs):
          raise NotImplementedError()
      async def read(self, filename):
-         raise NotImplementedError()
+         if b"\0" in filename:
+             raise ValueError("filename contains null charactor")
+         if b"\n" in filename:
+             raise ValueError("filename contains newline")
+ 
+         self._process.stdin.write(b"read %b\n" % filename)
+ 
+         result = b"";
+         while True:
+             line = await self._process.stdout.readuntil()
+             if line == b"ok\n":
+                 return result
+             if line == b"error\n":
+                 raise asyncio.IncompleteReadError(result, None)
+             count = int(line)
+             result += await self._process.stdout.readexactly(count)
+ 
      async def write(self, *args, **kwargs):
          raise NotImplementedError()
  
Implement read of Python wrapper
## Code Before:
import asyncio

class Sandbox:
    def __init__(self):
        self._process = None
    async def start(self):
        if self._process is not None:
            raise ValueError("The sandbox has started")
        self._process = await asyncio.create_subprocess_exec(
                "sandbox",
                stdin = asyncio.subprocess.PIPE,
                stdout = asyncio.subprocess.PIPE)
    async def close(self):
        if self._process is None:
            raise ValueError("The sandbox has not started")
        if self._process.returncode is not None:
            return
        self._process.stdin.close()
        await self._process.wait()

    async def __aenter__(self):
        await self.start()
        return self
    async def __aexit__(self, exc_type, exc, tb):
        await self.close()

    async def execute(self, *args, **kwargs):
        raise NotImplementedError()
    async def read(self, filename):
        raise NotImplementedError()
    async def write(self, *args, **kwargs):
        raise NotImplementedError()

## Instruction:
Implement read of Python wrapper
## Code After:
import asyncio

class Sandbox:
    def __init__(self):
        self._process = None
    async def start(self):
        if self._process is not None:
            raise ValueError("The sandbox has started")
        self._process = await asyncio.create_subprocess_exec(
                "sandbox",
                stdin = asyncio.subprocess.PIPE,
                stdout = asyncio.subprocess.PIPE)
    async def close(self):
        if self._process is None:
            raise ValueError("The sandbox has not started")
        if self._process.returncode is not None:
            return
        self._process.stdin.close()
        await self._process.wait()

    async def __aenter__(self):
        await self.start()
        return self
    async def __aexit__(self, exc_type, exc, tb):
        await self.close()

    async def execute(self, *args, **kwargs):
        raise NotImplementedError()
    async def read(self, filename):
        if b"\0" in filename:
            raise ValueError("filename contains null charactor")
        if b"\n" in filename:
            raise ValueError("filename contains newline")

        self._process.stdin.write(b"read %b\n" % filename)

        result = b"";
        while True:
            line = await self._process.stdout.readuntil()
            if line == b"ok\n":
                return result
            if line == b"error\n":
                raise asyncio.IncompleteReadError(result, None)
            count = int(line)
            result += await self._process.stdout.readexactly(count)

    async def write(self, *args, **kwargs):
        raise NotImplementedError()
