input: Write a python function to extract keys from a dictionary and return them as a list.
  assert extract_keys({'Name': 'Alice', 'Address': '123 Main St', 'Phone': '555-5555'}) == ['Name', 'Address', 'Phone']
  assert extract_keys({'Age': 30, 'Gender': 'Female', 'Occupation': 'Engineer'}) == ['Age', 'Gender', 'Occupation']
  assert extract_keys({'Country': 'USA', 'State': 'California'}) == ['Country', 'State']
output: def extract_keys(d):
      return list(d.keys())