<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def incr(self, key, value, noreply=False):
 """ The memcached "incr" command. Args: key: str, see class docs for details. value: int, the amount by which to increment the value. noreply: optional bool, False to wait for the reply (the default). Returns: If noreply is True, always returns None. Otherwise returns the new value of the key, or None if the key wasn't found. """

        key = self.check_key(key)
        cmd = b'incr ' + key + b' ' + six.text_type(value).encode('ascii')
        if noreply:
            cmd += b' noreply'
        cmd += b'\r\n'
        results = self._misc_cmd([cmd], b'incr', noreply)
        if noreply:
            return None
        if results[0] == b'NOT_FOUND':
            return None
        return int(results[0])