"u" symbols followed by a "g" symbol together. Next, "ug" is added to the vocabulary. The set of words then
becomes
("h" "ug", 10), ("p" "ug", 5), ("p" "u" "n", 12), ("b" "u" "n", 4), ("h" "ug" "s", 5)
BPE then identifies the next most common symbol pair. It's "u" followed by "n", which occurs 16 times. "u",
"n" is merged to "un" and added to the vocabulary. The next most frequent symbol pair is "h" followed by
"ug", occurring 15 times. Again the pair is merged and "hug" can be added to the vocabulary.
At this stage, the vocabulary is ["b", "g", "h", "n", "p", "s", "u", "ug", "un", "hug"] and our set of unique words
is represented as
("hug", 10), ("p" "ug", 5), ("p" "un", 12), ("b" "un", 4), ("hug" "s", 5)
Assuming, that the Byte-Pair Encoding training would stop at this point, the learned merge rules would then be applied
