code: def all_reference_commits(self):
          
          return CommitsDataFrame(self._engine_dataframe.getAllReferenceCommits(), self._session, self._implicits)
docs: Returns the current DataFrame joined with the commits DataFrame, with all of the commits
          in all references.
  
          >>> commits_df = refs_df.all_reference_commits
  
          Take into account that getting all the commits will lead to a lot of repeated tree
          entries and blobs, thus making your query very slow.
  
          Most of the time, you just want the HEAD commit of each reference:
  
          >>> commits_df = refs_df.commits
  
          :rtype: CommitsDataFrame