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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def check_data(self):
 """Check that definitions file is present, and that faces file is readable."""

        assert os.path.exists(self.data_fp)
        if gis:
            with fiona.drivers():
                with fiona.open(self.faces_fp) as src:
                    assert src.meta

        gpkg_hash = json.load(open(self.data_fp))['metadata']['sha256']
        assert gpkg_hash == sha256(self.faces_fp)