checks whether the string has the specified prefix
None
| std::has_prefix | returns *true* if the second argument is a prefix of the first argument | 
| std_types::string/std::has_suffix | checks whether the string has the specified suffix | 
| std_types::string/std::without_prefix | returns the string without the specified prefix | 
| std_types::string/std::contains | succeeds if the specified expression occurrs at least once within the string |