If the user is trying to change Matplotlib backends with
        %matplotlib, send the same command again to the kernel to
        correctly change it.

        Fixes issue 4002

def change_mpl_backend(self, command):
        """
        If the user is trying to change Matplotlib backends with
        %matplotlib, send the same command again to the kernel to
        correctly change it.

        Fixes issue 4002
        """
        if command.startswith('%matplotlib') and \
          len(command.splitlines()) == 1:
            if not 'inline' in command:
                self.silent_execute(command)