def get_chunk(self, size=None):
if size is None:<EOL><INDENT>size = self._chunksize<EOL><DEDENT>return self.read(nrows=size)<EOL>
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