code: def busday_count_mask_NaT(begindates, enddates, out=None):
      
      if out is None:
          out = empty(broadcast(begindates, enddates).shape, dtype=float)
  
      beginmask = isnat(begindates)
      endmask = isnat(enddates)
  
      out = busday_count(
          # Temporarily fill in non-NaT values.
          where(beginmask, _notNaT, begindates),
          where(endmask, _notNaT, enddates),
          out=out,
      )
  
      # Fill in entries where either comparison was NaT with nan in the output.
      out[beginmask | endmask] = nan
      return out
docs: Simple of numpy.busday_count that returns `float` arrays rather than int
      arrays, and handles `NaT`s by returning `NaN`s where the inputs were `NaT`.
  
      Doesn't support custom weekdays or calendars, but probably should in the
      future.
  
      See Also
      --------
      np.busday_count