code: def in_(this, that, axis=semantics.axis_default):
      
      this = as_index(this, axis=axis, lex_as_struct=True, base=True)
      that = as_index(that, axis=axis, lex_as_struct=True)
  
      left = np.searchsorted(that._keys, this._keys, sorter=that.sorter, side='left')
      right = np.searchsorted(that._keys, this._keys, sorter=that.sorter, side='right')
  
      return left != right
docs: Returns bool for each element of `this`, indicating if it is present in `that`
  
      Parameters
      ----------
      this : indexable key sequence
          sequence of items to test for
      that : indexable key sequence
          sequence of items to test against
  
      Returns
      -------
      ndarray, [that.size], bool
          returns a bool for each element in `this`, indicating if it is present in `that`
  
      Notes
      -----
      Reads as 'this in that'
      Similar to 'that contains this', but with different performance characteristics