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: bigtext_printer.go
    path of file: ./repos/pterm
    
    the code of the file until where you have to start completion: package pterm

import (
	"io"
	"strings"

	"github.com/gookit/color"

	"github.com/mattn/go-runewidth"

	"github.com/pterm/pterm/internal"
)

// Letters is a slice of Letter.
type Letters []Letter

// Letter is an object, which holds a string and a specific Style for it.
type Letter struct {
	String string
	Style  *Style
	RGB    RGB
}

// WithStyle returns a new Letter with a specific Style.
func (l Letter) WithStyle(style *Style) *Letter {
	l.Style = style
	return &l
}

// WithRGB returns a new Letter with a specific RGB color (overwrites style).
func 
    
func (p BigTextPrinter) Srender() (string, error) {
	var ret string

	if RawOutput {
		for _, letter := range p.Letters {
			ret += letter.String
		}
		return ret, nil
	}

	var bigLetters Letters
	for _, l := range p.Letters {
		if val, ok := p.BigCharacters[l.String]; ok {
			bigLetters = append(bigLetters, Letter{
				String: val,
				Style:  l.Style,
				RGB:    l.RGB,
			})
		}
	}

	var maxHeight int

	for _, l := range bigLetters {
		h := strings.Count(l.String, "\n")
		if h > maxHeight {
			maxHeight = h
		}
	}

	for i := 0; i <= maxHeight; i++ {
		for _, letter := range bigLetters {
			var letterLine string
			letterLines := strings.Split(letter.String, "\n")
			maxLetterWidth := internal.GetStringMaxWidth(letter.String)
			if len(letterLines) > i {
				letterLine = letterLines[i]
			}
			letterLineLength := runewidth.StringWidth(letterLine)
			if letterLineLength < maxLetterWidth {
				letterLine += strings.Repeat(" ", maxLetterWidth-letterLineLength)
			}

			if letter.RGB != (RGB{}) && (color.IsSupportRGBColor() || internal.RunsInCi()) {
				ret += letter.RGB.Sprint(letterLine)
			} else {
				ret += letter.Style.Sprint(letterLine)
			}
		}
		ret += "\n"
	}

	return ret, nil
}