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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 _get_memmap(self):
 """Get the memory map for the SEVIRI data"""


        with open(self.filename) as fp:

            data_dtype = self._get_data_dtype()
            hdr_size = native_header.itemsize

            return np.memmap(fp, dtype=data_dtype,
                             shape=(self.mda['number_of_lines'],),
                             offset=hdr_size, mode="r")