Xcode iOS app build fails due to MXSendReplyEventStringLocalizer protocol - swift

Question

I'm an Xcode newbie. I'm using non-modified Swift source code from the Github project that is 100% working itself as it's released to public.
I installed pods for it.
When trying to build this non-modified testing app in xCode, it fails with:
MXKSendReplyEventStringLocalizer.swift:19:7 Type 'MXKSendReplyEventStringLocalizer' does not conform to protocol 'MXSendReplyEventStringLocalizerProtocol'
As the code itself should be working out of the box, I suppose the issue is caused by my Mac's environment.
if I select "Fix" in the problematic code block (adding protocol stubs offered by Xcode), this error disappears on the next build attempt, but new ones appear, I. believe because the placeholder was set by selecting "Fix" previously.
Command SwiftEmitModule failed with a nonzero exit code
About this code:
_class MXKSendReplyEventStringLocalizer: NSObject, MXSendReplyEventStringLocalizerProtocol {
func replyToEndedPoll() -> String {
<#code#>
}
Any advise what direction to investigate is appreciated. Searching other threads related to MXSendReplyEventStringLocalizer didn't help.
Here is the problematic code block** that is highlighted by Xcode on the initial build:
import Foundation
class MXKSendReplyEventStringLocalizer: NSObject, MXSendReplyEventStringLocalizerProtocol {
func senderSentAnImage() -> String {
VectorL10n.messageReplyToSenderSentAnImage
}
func senderSentAVideo() -> String {
VectorL10n.messageReplyToSenderSentAVideo
}