def update(self, old_line, new_line, once=False):
nb = <NUM_LIT:0><EOL>for block in self.blocks:<EOL><INDENT>nb += block.update(old_line, new_line, once=once)<EOL>if nb and once:<EOL><INDENT>return nb<EOL><DEDENT><DEDENT>return nb<EOL>
Replace all lines matching `old_line` with `new_line`.

        If ``once`` is set to True, remove only the first instance.