code: def delete_left(elem1, elem2):
      
      # assert not (nested(elem1, elem2) or nested(elem2, elem1)), 'deletion not defined for nested elements'
      if overlapping_right(elem1, elem2):
          elem1['end'] = elem2['start']
      return elem1, elem2
docs: xxxxx
         yyyyy
      ---------
      xxx
         yyyyy