if let filenameRange = line.range(of: "filename=", options: caseInsensitiveSearch, range: labelRange.upperBound..<line.endIndex) {
                let valueStartIndex = line.index(after: filenameRange.upperBound)
                let valueEndIndex = line.range(of: "\"", range: valueStartIndex..<line.endIndex)
                part.filename = String(line[valueStartIndex..<(valueEndIndex?.lowerBound ?? line.endIndex)])
            }