Clear out large attributes from the metadata objects

def clear(self):
        """
        Clear out large attributes from the metadata objects
        """
        for sample in self.metadata:
            try:
                delattr(sample.depth, 'bases')
                delattr(sample.depth, 'coverage')
                delattr(sample.depth, 'length')
                delattr(sample.depth, 'stddev')
            except AttributeError:
                pass