Pauli products and Pauli product sums

PauliProduct(index[, num_qubits])	A tensor product of Pauli operators.
SparsePauliSum(indices, coeffs[, ...])	Purpose-specific implementation of a sparse Pauli operator.
SparsePauliSumArray([pauli_sums, ...])	A container of SparsePauliSums with concatenated data.