docs: def fix_tags_on_cands_missing_reals(user_id, vos_dir, property):
      "At the moment this just checks for a single user's missing reals. Easy to generalise it to all users."
      con = context.get_context(vos_dir)
      user_progress = []
      listing = con.get_listing(tasks.get_suffix('reals'))
      mpc_listing = con.get_listing('mpc')
      for filename in listing:
          if not filename.startswith('fk'):
              user = storage.get_property(con.get_full_path(filename), property)
              if (user is not None):
                  # and (user == user_id):  # modify 'and' to generalise to all users with work in this directory
                  #realsfile = filename.replace('cands', 'reals')
                  #if not con.exists(realsfile):
                  #    print filename, 'no reals file', realsfile
  
                  # go through the listing of .mpc files and see if any match this reals.astrom
                  is_present = False
                  for mpcfile in [f for f in mpc_listing if not f.startswith('fk')]:
                      if mpcfile.startswith(filename):
                          print filename, user, 'exists!', mpcfile
                          is_present = True
  
                  if not is_present:
                      user_progress.append(filename)
                      print filename, user, 'no mpc file'
                      storage.set_property(con.get_full_path(filename), property, None)
  
      print 'Fixed files:', len(user_progress)
  
      return