code: func (f *Field) Range(name string, op pql.Token, predicate int64) (*Row, error) {
  	// Retrieve and validate bsiGroup.
  	bsig := f.bsiGroup(name)
  	if bsig == nil {
  		return nil, ErrBSIGroupNotFound
  	} else if predicate < bsig.Min || predicate > bsig.Max {
  		return nil, nil
  	}
  
  	// Retrieve bsiGroup's view.
  	view := f.view(viewBSIGroupPrefix + name)
  	if view == nil {
  		return nil, nil
  	}
  
  	baseValue, outOfRange := bsig.baseValue(op, predicate)
  	if outOfRange {
  		return NewRow(), nil
  	}
  
  	return view.rangeOp(op, bsig.BitDepth(), baseValue)
  }
docs: // Range performs a conditional operation on Field.