In this task, you need to reverse all words of a given length in the sentence. The number of letters in a word determine its length. For example, the length of the word "apple" is 5.

Example Input: Sentence: 'a close up of the front of a train on train tracks'. Reverse all words of length '3' in the given sentence.
Example Output: a close up of eht front of a train on train tracks

Example Input: Sentence: 'a bunch of umbrellas are up in the air'. Reverse all words of length '9' in the given sentence.
Example Output: a bunch of sallerbmu are up in the air

Example Input: Sentence: 'a policeman in a yellow vest stands outside'. Reverse all words of length '4' in the given sentence.
Example Output:
a policeman in a yellow tsev stands outside