code: def add_to_file_links(self):
          # type: () -> None
          '''
          Increment the number of POSIX file links on this entry by one.
  
          Parameters:
           None.
          Returns:
           Nothing.
          '''
          if not self._initialized:
              raise pycdlibexception.PyCdlibInternalError('Rock Ridge extension not yet initialized')
  
          if self.dr_entries.px_record is None:
              if self.ce_entries.px_record is None:
                  raise pycdlibexception.PyCdlibInvalidInput('No Rock Ridge file links')
              self.ce_entries.px_record.posix_file_links += 1
          else:
              self.dr_entries.px_record.posix_file_links += f add_to_file_links(self):
          # type: () -> None
          '''
          Increment the number of POSIX file links on this entry by one.
  
          Parameters:
           None.
          Returns:
           Nothing.
          '''
          if not self._initialized:
              raise pycdlibexception.PyCdlibInternalError('Rock Ridge extension not yet initialized')
  
          if self.dr_entries.px_record is None:
              if self.ce_entries.px_record is None:
                  raise pycdlibexception.PyCdlibInvalidInput('No Rock Ridge file links')
              self.ce_entries.px_record.posix_file_links += 1
          else:
              self.dr_entries.px_record.posix_file_links += 1
docs: Increment the number of POSIX file links on this entry by one.
  
          Parameters:
           None.
          Returns:
           Nothing.