input: Write a python function to extract keys from a dictionary.
  assert extract_keys(myDict) == ['name', 'age', 'height', 'city', 'job']
  assert extract_keys({'a': 1, 'b': 2, 'c': 3}) == ['a', 'b', 'c']
  assert extract_keys({}) == []
output: def extract_keys(d):
      return list(d.keys())