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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(self):
 """ Returns the first meaningful object in this filter. """

        if not self.subfilters:
            # No sub-filters
            return None

        # New sub-filters list
        new_filters = []
        for subfilter in self.subfilters:
            # Normalize the sub-filter before storing it
            norm_filter = subfilter.normalize()
            if norm_filter is not None and norm_filter not in new_filters:
                new_filters.append(norm_filter)

        # Update the instance
        self.subfilters = new_filters

        size = len(self.subfilters)
        if size > 1 or self.operator == NOT:
            # Normal filter or NOT
            # NOT is the only operator to accept 1 operand
            return self

        # Return the only child as the filter object
        return self.subfilters[0].normalize()