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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def __read_block(self, size):
 """Read a block of 'size' bytes from the server. An internal buffer is used to read data from the server. If enough data is available from it, we return that data. Eventually, we try to grab the missing part from the server for Client.read_timeout seconds. If no data can be retrieved, it is considered as a fatal error and an 'Error' exception is raised. :param size: number of bytes to read :rtype: string :returns: the read block (can be empty) """

        buf = b""
        if len(self.__read_buffer):
            limit = (
                size if size <= len(self.__read_buffer) else
                len(self.__read_buffer)
            )
            buf = self.__read_buffer[:limit]
            self.__read_buffer = self.__read_buffer[limit:]
            size -= limit
        if not size:
            return buf
        try:
            buf += self.sock.recv(size)
        except (socket.timeout, ssl.SSLError):
            raise Error("Failed to read %d bytes from the server" % size)
        self.__dprint(buf)
        return buf