'Handle a known-indent text block. Extend or override in subclasses.
Recursively run the registered state machine for known-indent indented
blocks (`self.known_indent_sm`). The indent is the length of the
match, ``match.end()``.'

def known_indent(self, match, context, next_state):

    (indented, line_offset, blank_finish) = self.state_machine.get_known_indented(match.end())
    sm = self.known_indent_sm(debug=self.debug, **self.known_indent_sm_kwargs)
    results = sm.run(indented, input_offset=line_offset)
    return (context, next_state, results)
