code: def get_udiff(filenode_old, filenode_new, show_whitespace=True):
      
      try:
          filenode_old_date = filenode_old.changeset.date
      except NodeError:
          filenode_old_date = None
  
      try:
          filenode_new_date = filenode_new.changeset.date
      except NodeError:
          filenode_new_date = None
  
      for filenode in (filenode_old, filenode_new):
          if not isinstance(filenode, FileNode):
              raise VCSError("Given object should be FileNode object, not %s"
                  % filenode.__class__)
  
      if filenode_old_date and filenode_new_date:
          if not filenode_old_date < filenode_new_date:
              logging.debug("Generating udiff for filenodes with not increasing "
                  "dates")
  
      vcs_udiff = unified_diff(filenode_old.content.splitlines(True),
                                 filenode_new.content.splitlines(True),
                                 filenode_old.name,
                                 filenode_new.name,
                                 filenode_old_date,
                                 filenode_old_date)
      return vcs_udiff
docs: Returns unified diff between given ``filenode_old`` and ``filenode_new``.