Definition: In this task, you need to remove 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 beagles are penned in but two have pushed their heads through the openings in the splintery wood slats'. Remove all words of length '7' in the given sentence.

the are penned in but two have pushed their heads the openings in the splintery wood slats