Remove qubit by projecting onto sector.

Takes a QubitOperator, and projects out a list of qubits, into either the +1 or -1 sector. Note - this requires knowledge of which sector we wish to project into.

operator the QubitOperator to work on
qubits a list of indices of qubits in operator to remove
sectors for each qubit, whether to project into the 0 subspace (=1) or the 1 subspace (=-1).

projected_operator the resultant operator

TypeError operator must be a QubitOperator.
TypeError qubits and sector must be an array-like.
ValueError If qubits and sectors have different length.
ValueError If sector are not specified as 0 or 1.