nl: _ with an argument string "Enter a valid 'slug' consisting of letters, numbers, underscores or hyphens.", and string 'invalid'. call the re.compile function with an argument raw string '^(25[0-5]|2[0-4]\d|[0-1]?\d?\d)(\.(25[0-5]|2[0-4]\d|[0-1]?\d?\d)){3}$',
code: ipv4_re = re . compile ( r'^(25[0-5]|2[0-4]\d|[0-1]?\d?\d)(\.(25[0-5]|2[0-4]\d|[0-1]?\d?\d)){3}$' )