input: Write a python function to extract words from a given string.
  assert find_words("This is a sample string") == ["This", "is", "a", "sample", "string"]
  assert find_words("Hello, world!") == ["Hello", "world"]
  assert find_words("No delimiters") == ["No", "delimiters"]
  assert find_words("123 456") == []
output: def find_words(s):
      import re
      return [word for word in re.findall(r'\b\w+\b', s) if word.isalpha()]