code: def _numeric_summary(arg, exact_nunique=False, prefix=None):
      
      metrics = [
          arg.count(),
          arg.isnull().sum().name('nulls'),
          arg.min(),
          arg.max(),
          arg.sum(),
          arg.mean(),
      ]
  
      if exact_nunique:
          unique_metric = arg.nunique().name('nunique')
      else:
          unique_metric = arg.approx_nunique().name('approx_nunique')
  
      metrics.append(unique_metric)
      return _wrap_summary_metrics(metrics, prefix)
docs: Compute a set of summary metrics from the input numeric value expression
  
      Parameters
      ----------
      arg : numeric value expression
      exact_nunique : boolean, default False
      prefix : string, default None
        String prefix for metric names
  
      Returns
      -------
      summary : (count, # nulls, min, max, sum, mean, nunique)