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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 default(self, obj):

 """Implement this method in a subclass such that it returns a tree for ``o``."""

        if isinstance(obj, BioCDocument):
            return encode_document(obj)
        if isinstance(obj, BioCCollection):
            return encode_collection(obj)
        raise TypeError(f'Object of type {obj.__class__.__name__} is not BioC XML serializable')