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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 first_fit(self, train_x, train_y):
 """ Fit the regressor for the first time. """

        train_x, train_y = np.array(train_x), np.array(train_y)

        self._x = np.copy(train_x)
        self._y = np.copy(train_y)

        self._distance_matrix = edit_distance_matrix(self._x)
        k_matrix = bourgain_embedding_matrix(self._distance_matrix)
        k_matrix[np.diag_indices_from(k_matrix)] += self.alpha

        self._l_matrix = cholesky(k_matrix, lower=True)  # Line 2

        self._alpha_vector = cho_solve((self._l_matrix, True), self._y)  # Line 3

        self._first_fitted = True
        return self