@synchronized<EOL><INDENT>def delete_date(self, date):<DEDENT>
self.lines = [<EOL>line for line in self.lines<EOL>if not isinstance(line, DateLine) or line.date != date<EOL>]<EOL>self.lines = trim(self.lines)<EOL>
Remove the date line from the textual representation. This doesn't
remove any entry line.