input: Write a python function to print lines from a file that are shorter than a given number.
  assert filter_lines_by_length('sample.txt', 10) == ['short\n', 'tiny\n']
  assert filter_lines_by_length('sample.txt', 5) == ['tiny\n']
  assert filter_lines_by_length('example.txt', 15) == ['example line\n', 'shorter\n']
output: def filter_lines_by_length(filename, length):
      with open(filename, 'r') as file:
          lines = file.readlines()
      return [line for line in lines if len(line) < length]