code: def do_hdr(self, line, hdrs_usr):
          
          # If there is no header hint, consider the first line the header.
          if self.hdr_ex is None:
              self._init_hdr(line, hdrs_usr)
              return True
          # If there is a header hint, examine each beginning line until header hint is found.
          elif self.hdr_ex in line:
              self._init_hdr(line, hdrs_usr)
              return True
          return False
docs: Initialize self.h2i.