docs: def add_entry(self, date, entry):
          """
          Add the given entry to the textual representation.
          """
          in_date = False
          insert_at = 0
  
          for (lineno, line) in enumerate(self.lines):
              # Search for the date of the entry
              if isinstance(line, DateLine) and line.date == date:
                  in_date = True
                  # Insert here if there is no existing Entry for this date
                  insert_at = lineno
                  continue
  
              if in_date:
                  if isinstance(line, Entry):
                      insert_at = lineno
                  elif isinstance(line, DateLine):
                      break
  
          self.lines.insert(insert_at + 1, entry)
  
          # If there's no other Entry in the current date, add a blank line
          # between the date and the entry
          if not isinstance(self.lines[insert_at], Entry):
              self.lines.insert(insert_at + 1, TextLine(''))