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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 validate(self):
 """Ensure that the Backtrack block is valid."""

        validate_marked_location(self.location)
        if not isinstance(self.optional, bool):
            raise TypeError(u'Expected bool optional, got: {} {}'.format(
                type(self.optional).__name__, self.optional))