def readline(self, fmt=None):
prefix_size = self._fix()<EOL>if fmt is None:<EOL><INDENT>content = self.read(prefix_size)<EOL><DEDENT>else:<EOL><INDENT>fmt = self.endian + fmt<EOL>fmt = _replace_star(fmt, prefix_size)<EOL>content = struct.unpack(fmt, self.read(prefix_size))<EOL><DEDENT>try:<EOL><INDENT>suffix_size = self._fix()<EOL><DEDENT>except EOFError:<EOL><INDENT>suffix_size = -<NUM_LIT:1><EOL><DEDENT>if prefix_size != suffix_size:<EOL><INDENT>raise IOError(_FIX_ERROR)<EOL><DEDENT>return content<EOL>
Return next unformatted "line". If format is given, unpack content,
otherwise return byte string.