input: Write a python function to strip leading and trailing whitespaces from a string.
  assert strip_whitespace("  Hello World  ") == "Hello World"
  assert strip_whitespace("    Python is great!   ") == "Python is great!"
  assert strip_whitespace("\tTrim this text\t") == "Trim this text"
output: def strip_whitespace(s):
      return s.strip()