'Similar to L{ITransport.write} but also allows the file descriptor in
the child process which will receive the bytes to be specified.
This implementation is limited to writing to the child\'s standard input.
@param fd: The file descriptor to which to write.  Only stdin (C{0}) is
supported.
@type fd: C{int}
@param data: The bytes to write.
@type data: C{bytes}
@return: L{None}
@raise KeyError: If C{fd} is anything other than the stdin file
descriptor (C{0}).'

def writeToChild(self, fd, data):

    if (fd == 0):
        self.stdin.write(data)
    else:
        raise KeyError(fd)
