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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 save(cls,instance,filename):
 """Class method save for saving TracingVariable."""

        filename = cls.correct_file_extension(filename)
        try:
            with open(filename,'wb') as f:
                pickle.dump(instance,f,protocol=pickle.HIGHEST_PROTOCOL)
        except MemoryError as e:
            print ('{} occurred, will downsampled the saved file by 20.'
                   .format(type(e).__name__))
            copy_instance = instance.copy()
            copy_instance.H = copy_instance.H[::20,:,:]
            copy_instance.Y = copy_instance.Y[::20,:]
            with open(filename,'wb') as f:
                pickle.dump(copy_instance,f,protocol=pickle.HIGHEST_PROTOCOL)