input: Write a function to validate IPv4 addresses.
  assert validate_ipv4_address('192.168.0.1') == True
  assert validate_ipv4_address('255.255.255.255') == True
  assert validate_ipv4_address('0.0.0.0') == True
  assert validate_ipv4_address('256.256.256.256') == False
  assert validate_ipv4_address('123.456.78.90') == False
output: def validate_ipv4_address(address):
      parts = address.split('.')
      if len(parts) != 4:
          return False
      for part in parts:
          if not part.isdigit():
              return False
          num = int(part)
          if num < 0 or num > 255:
              return False
      return True