code: def intervalsubtract(left, right, lstart='start', lstop='stop', rstart='start',
                       rstop='stop', lkey=None, rkey=None, include_stop=False):
      
  
      assert (lkey is None) == (rkey is None), \
          'facet key field must be provided for both or neither table'
      return IntervalSubtractView(left, right, lstart=lstart, lstop=lstop,
                                  rstart=rstart, rstop=rstop, lkey=lkey,
                                  rkey=rkey, include_stop=include_stop)
docs: Subtract intervals in the right hand table from intervals in the left hand 
      table.