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: 'a mailing package in a white package with a blue frisbee on the outside'. Reverse all words of length '7' in the given sentence.

a gniliam egakcap in a white egakcap with a blue eebsirf on the edistuo