TASK 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.
PROBLEM: Sentence: 'a green apple and knife on dark wooden stairs'. Reverse all words of length '3' in the given sentence.

SOLUTION: a green apple dna knife on dark wooden stairs

PROBLEM: Sentence: 'a very small shiny metal cup with some food in it'. Reverse all words of length '4' in the given sentence.

SOLUTION: a yrev small shiny metal cup htiw emos doof in it

PROBLEM: Sentence: 'the horse is being held still with a halter'. Reverse all words of length '2' in the given sentence.

SOLUTION:
the horse si being held still with a halter