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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 extract(self):
 """ Creates a copy of this tabarray in the form of a numpy ndarray. Useful if you want to do math on array elements, e.g. if you have a subset of the columns that are all numerical, you can construct a numerical matrix and do matrix operations. """

        return np.vstack([self[r] for r in self.dtype.names]).T.squeeze()