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 back of a car on a street side with a purple umbrella lying beside it'. Reverse all words of length '6' in the given sentence.

the back of a car on a teerts side with a elprup umbrella lying ediseb it