input: Write a python function to count the 10 most common words in a list of sentences.
  assert count_most_common_words(["This is a text about dogs", "This is a text about cats"]) == [('This', 2), ('is', 2), ('a', 2), ('text', 2), ('about', 2), ('dogs', 1), ('cats', 1)]
  assert count_most_common_words(["apple apple banana", "banana apple"]) == [('apple', 3), ('banana', 2)]
  assert count_most_common_words(["one two three", "four five six", "seven eight nine ten"]) == [('one', 1), ('two', 1), ('three', 1), ('four', 1), ('five', 1), ('six', 1), ('seven', 1), ('eight', 1), ('nine', 1), ('ten', 1)]
output: def count_most_common_words(sentences):
      from collections import Counter
      from itertools import chain
  
      # Split each sentence into words and flatten the list of lists
      words = list(chain.from_iterable(sentence.split() for sentence in sentences))
      
      # Use Counter to count the frequency of each word
      counter = Counter(words)
      
      # Get the 10 most common words
      most_common = counter.most_common(10)
      
      return most_common