code: def generator_between(self, begin: int, end: int) -> Iterator[str]:
          
  
          s: str = self.content[begin:end + 1]
          for line in s:
              yield line
docs: Create a generate that iterates the whole content of the file or string, starting from *begin* index,
          end by *end* index. **Not byte!**
  
          :param begin: An integer labels the starting index.
          :param end: An integer labels the ending index.
          :return: An iterator of string.