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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 normalize(filename):
 """Return an absolute path of the given file name."""

        # Default value means we do not resolve a model file.
        if filename == "default":
            return filename
        filename = expanduser(filename)
        if isabs(filename):
            return filename
        else:
            return join(os.getcwd(), filename)