code: def _length(df, *args, **kwargs):
      return float(len(df))
  
file_path: lkpy/lenskit/topn.py
imports: import logging
  import functools
  import numpy
  import pandas
  from .metrics.topn import *
  from .util import Stopwatch
label_desc: Use image node_id 1 for calling a global function with example usage: _length(df) and returns: float