You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: shared.go
    path of file: ./repos/istio/operator/pkg/manifest
    
    the code of the file until where you have to start completion: // Copyright Istio Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
/
    
func readLayeredYAMLs(filenames []string, stdinReader io.Reader) (string, error) {
	var ly string
	var stdin bool
	for _, fn := range filenames {
		var b []byte
		var err error
		if fn == "-" {
			if stdin {
				continue
			}
			stdin = true
			b, err = io.ReadAll(stdinReader)
		} else {
			b, err = os.ReadFile(strings.TrimSpace(fn))
		}
		if err != nil {
			return "", err
		}
		multiple := false
		multiple, err = hasMultipleIOPs(string(b))
		if err != nil {
			return "", err
		}
		if multiple {
			return "", fmt.Errorf("input file %s contains multiple IstioOperator CRs, only one per file is supported", fn)
		}
		ly, err = util.OverlayIOP(ly, string(b))
		if err != nil {
			return "", err
		}
	}
	return ly, nil
}