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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 remove_annotation(self, a):
 """ Removes an annotation from this AST. :param a: the annotation to remove :returns: a new AST, with the annotation removed """

        return self._apply_to_annotations(lambda alist: tuple(oa for oa in alist if oa != a))