// add underscore if last letter is capital letter
		// add underscore when previous letter is lowercase
		// add underscore when next letter is lowercase
		if (i != 0 || i == l-1) && ((i > 0 && rune(camel[i-1]) >= 'a') ||
			(i < l-1 && rune(camel[i+1]) >= 'a')) {
			b.WriteRune('_')
		}
		b.WriteRune(v + 'a' - 'A')
	}
	return b.String()

							w.Header().Set(k, v)
						}

						if opts.PartNumber > 0 && strings.Contains(ci.ETag, "-") {
							w.Header()[xhttp.AmzMpPartsCount] = []string{
								strings.TrimLeftFunc(ci.ETag, func(r rune) bool {
									return !unicode.IsNumber(r)
								}),
							}
						}

						// For providing ranged content
						start, rangeLen, err := rs.GetOffsetLength(ci.Size)
						if err != nil {