'Toggle overwrite mode. With an explicit positive numeric
argument, switches to overwrite mode. With an explicit non-positive
numeric argument, switches to insert mode. This command affects only
emacs mode; vi mode does overwrite differently. Each call to
readline() starts in insert mode. In overwrite mode, characters
bound to self-insert replace the text at point rather than pushing
the text to the right. Characters bound to backward-delete-char
replace the character before point with a space.'

def overwrite_mode(self, e):

    pass
