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: 'cows in pasture staring toward the camera with trees in background'. Reverse all words of length '7' in the given sentence.

cows in erutsap gnirats toward the camera with trees in background