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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 extend(self, polymer):
 """Extends the `Polymer` with the contents of another `Polymer`. Notes ----- Does not update labelling. """

        if isinstance(polymer, Polymer):
            self._monomers.extend(polymer)
        else:
            raise TypeError(
                'Only Polymer objects may be merged with a Polymer using unary operator "+".')
        return