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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 get_block_type(self, def_id):
 """Get a block_type by its definition id."""

        try:
            return self._definitions[def_id]
        except KeyError:
            try:
                return def_id.aside_type
            except AttributeError:
                raise NoSuchDefinition(repr(def_id))