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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_file(self, filename):
 """Get file source from cache"""

        import linecache
        # Hack for frozen importlib bootstrap
        if filename == '<frozen importlib._bootstrap>':
            filename = os.path.join(
                os.path.dirname(linecache.__file__), 'importlib',
                '_bootstrap.py'
            )
        return to_unicode_string(
            ''.join(linecache.getlines(filename)), filename
        )