code: def at_line(self, line: FileLine) -> Iterator[InsertionPoint]:
          
          logger.debug("finding insertion points at line: %s", str(line))
          filename = line.filename  # type: str
          line_num = line.num  # type: int
          for ins in self.in_file(filename):
              if line_num == ins.location.line:
                  logger.debug("found insertion point at line [%s]: %s",
                               str(line), ins)
                  yield ins
docs: Returns an iterator over all of the insertion points located at a
          given line.