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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 project_op(self, op):
 """ Project an operator onto the basis. :param qutip.Qobj op: The operator to project. :return: The projection coefficients as a numpy array. :rtype: scipy.sparse.csr_matrix """

        if not self.is_orthonormal():  # pragma no coverage
            raise ValueError("project_op only implemented for orthonormal operator bases")
        return self.basis_transform.H * qt.operator_to_vector(op).data