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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 open_file(self, fname, length=None, offset=None, swap=None, block=None, peek=None):
        '''
        Opens the specified file with all pertinent configuration settings.
        '''
        if length is None:
            length = self.length
        if offset is None:
            offset = self.offset
        if swap is None:
            swap = self.swap_size

        return binwalk.core.common.BlockFile(fname,
                                             subclass=self.subclass,
                                             length=length,
                                             offset=offset,
                                             swap=swap,
                                             block=block,
                                             peek=peek)