Haskell:

groupErrors :: (Ord a, Ord b) => [[(a, [b])]] -> [(a, [b])]
groupErrors =
  map (\vs -> (fst . head $ vs, concat . map (\(_,val) -> val) $ vs))
  . L.groupBy (\(a,_) (b,_) -> a == b)
  . L.sort
  . concat

CSS:

pre[class*='language-'] > code[data-language] {
	overflow: scroll;
	max-height: 28em;
	display: block;
}
pre[class*='language-'] > code[data-language]::before {
	content: attr(data-language);
	color: black;
	background-color: #CFCFCF;
	display: inline-block;
	position: absolute;
	top: 0;
	right: 0;
	font-size: 0.9em;
	border-radius: 0 0 0 5px;
	padding: 0 0.5em;
	text-shadow: none;
}

Java:

class OrphanBlock {
        final Block block;
        final List filteredTxHashes;
        final Map<Sha256Hash, Transaction> filteredTxn;
        OrphanBlock(Block block, @Nullable List filteredTxHashes, @Nullable Map<Sha256Hash, Transaction> filteredTxn) {
            final boolean filtered = filteredTxHashes != null && filteredTxn != null;
            Preconditions.checkArgument((block.transactions == null && filtered)
                                        || (block.transactions != null && !filtered));
            if (!shouldVerifyTransactions())
                this.block = block.cloneAsHeader();
            else
                this.block = block;
            this.filteredTxHashes = filteredTxHashes;
            this.filteredTxn = filteredTxn;
        }
}