Definition: 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.
Input: Sentence: 'the street sign underneath the stop sign has long icicles on it'. Reverse all words of length '6' in the given sentence.

the teerts sign underneath the stop sign has long icicles on it