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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 add(self, *blocks, indentation=0) -> "CodeBlock": """ Adds sub-blocks at the specified indentation level, which defaults to 0. Nones are skipped. Returns the parent block itself, useful for chaining. """

        for block in blocks:
            if block is not None:
                self._blocks.append((indentation, block))

        return self