code: func estimateUnknownSize(unk *runtime.Unknown, byteSize uint64) uint64 {
  	size := uint64(unk.Size())
  	// protobuf uses 1 byte for the tag, a varint for the length of the array (at most 8 bytes - uint64 - here),
  	// and the size of the array.
  	size += 1 + 8 + byteSize
  	return size
  }
docs: // estimateUnknownSize returns the expected bytes consumed by a given runtime.Unknown
  // object with a nil RawJSON struct and the expected size of the provided buffer. The
  // returned size will not be correct if RawJSOn is set on unk.