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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 append(self, annotation):
 """Add an annotation. Args: annotation (gkeepapi.node.Annotation):
 An Annotation object. Returns: gkeepapi.node.Annotation: The Annotation. """

        self._annotations[annotation.id] = annotation
        self._dirty = True
        return annotation