code: def get_chunk(self, size=None):
          
          if size is None:
              size = self._chunksize
          return self.read(nrows=size)
docs: Reads lines from Xport file and returns as dataframe
  
          Parameters
          ----------
          size : int, defaults to None
              Number of lines to read.  If None, reads whole file.
  
          Returns
          -------
          DataFrame