'unrecv(data)
Puts the specified data back at the beginning of the receive
buffer.
Examples:
>>> t = tube()
>>> t.recv_raw = lambda n: \'hello\'
>>> t.recv()
\'hello\'
>>> t.recv()
\'hello\'
>>> t.unrecv(\'world\')
>>> t.recv()
\'world\'
>>> t.recv()
\'hello\''

def unrecv(self, data):

    self.buffer.unget(data)
