code: def get_text_line(self, line_nb):
          
          # Taking into account the case when a file ends in an empty line,
          # since splitlines doesn't return that line as the last element
          # TODO: Make this function more efficient
          try:
              return to_text_string(self.toPlainText()).splitlines()[line_nb]
          except IndexError:
              return self.get_line_separator()
docs: Return text line at line number *line_nb*