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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 invoke_shell( self, term="vt100", width=80, height=24, width_pixels=0, height_pixels=0, environment=None, ):
 """ Start an interactive shell session on the SSH server. A new `.Channel` is opened and connected to a pseudo-terminal using the requested terminal type and size. :param str term: the terminal type to emulate (for example, ``"vt100"``) :param int width: the width (in characters) of the terminal window :param int height: the height (in characters) of the terminal window :param int width_pixels: the width (in pixels) of the terminal window :param int height_pixels: the height (in pixels) of the terminal window :param dict environment: the command's environment :return: a new `.Channel` connected to the remote shell :raises: `.SSHException` -- if the server fails to invoke a shell """

        chan = self._transport.open_session()
        chan.get_pty(term, width, height, width_pixels, height_pixels)
        chan.invoke_shell()
        return chan