<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def randombytes(n):
 """Return n random bytes."""

    # Use /dev/urandom if it is available.  Fall back to random module
    # if not.  It might be worthwhile to extend this function to use
    # other platform-specific mechanisms for getting random bytes.
    if os.path.exists("/dev/urandom"):
        f = open("/dev/urandom")
        s = f.read(n)
        f.close()
        return s
    else:
        L = [chr(random.randrange(0, 256)) for i in range(n)]
        return "".join(L)