old_contents: # -*- coding: utf-8 -*-
  # pylint: disable=invalid-name
  
  # Copyright 2017 IBM RESEARCH. All Rights Reserved.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  # =============================================================================
  
  """
  local_qiskit_simulator command to toggle noise off or on.
  """
  from qiskit import CompositeGate
  from qiskit import Gate
  from qiskit import QuantumCircuit
  from qiskit._instructionset import InstructionSet
  from qiskit._quantumregister import QuantumRegister
  
  
  class NoiseGate(Gate):
      """Simulator save operation."""
  
      def __init__(self, m, qubit, circ=None):
          """Create new save gate."""
          super().__init__("noise", [m], [qubit], circ)
  
      def qasm(self):
          """Return OPENQASM string."""
          qubit = self.arg[0]
          m = self.param[0]
          return self._qasmif("noise(%d) %s[%d];" % (m,
                                                     qubit[0].name,
                                                     qubit[1]))
  
      def inverse(self):
          """Invert this gate."""
          return self  # self-inverse
  
      def reapply(self, circ):
          """Reapply this gate to corresponding qubits in circ."""
          self._modifiers(circ.noise(self.param[0], self.arg[0]))
  
  
  def noise(self, m, q):
      """Cache the quantum state of locla_qiskit_simulator."""
      if isinstance(q, QuantumRegister):
          gs = InstructionSet()
          for j in range(q.size):
              gs.add(self.noise(m, (q, j)))
          return gs
      self._check_qubit(q)
      return self._attach(NoiseGate(m, q, self))
  
  
  # Add to QuantumCircuit and CompositeGate classes
  QuantumCircuit.noise = noise
  CompositeGate.noise = noise
  
  # Add to QASM header for parsing
  QuantumCircuit.header += "\ngate noise(m) a {}" + \
      "  // (local_qiskit_simulator) switch noise off (0) or on (1)"
  
new_contents: # -*- coding: utf-8 -*-
  # pylint: disable=invalid-name
  
  # Copyright 2017 IBM RESEARCH. All Rights Reserved.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  # =============================================================================
  
  """
  local_qiskit_simulator command to toggle noise off or on.
  """
  from qiskit import CompositeGate
  from qiskit import Gate
  from qiskit import QuantumCircuit
  from qiskit._instructionset import InstructionSet
  from qiskit._quantumregister import QuantumRegister
  
  
  class NoiseGate(Gate):
      """Simulator save operation."""
  
      def __init__(self, m, qubit, circ=None):
          """Create new save gate."""
          super().__init__("noise", [m], [qubit], circ)
  
      def qasm(self):
          """Return OPENQASM string."""
          qubit = self.arg[0]
          m = self.param[0]
          return self._qasmif("noise(%d) %s[%d];" % (m,
                                                     qubit[0].name,
                                                     qubit[1]))
  
      def inverse(self):
          """Invert this gate."""
          return self  # self-inverse
  
      def reapply(self, circ):
          """Reapply this gate to corresponding qubits in circ."""
          self._modifiers(circ.noise(self.param[0], self.arg[0]))
  
  
  def noise(self, m, q):
      """Cache the quantum state of local_qiskit_simulator."""
      if isinstance(q, QuantumRegister):
          gs = InstructionSet()
          for j in range(q.size):
              gs.add(self.noise(m, (q, j)))
          return gs
      self._check_qubit(q)
      return self._attach(NoiseGate(m, q, self))
  
  
  # Add to QuantumCircuit and CompositeGate classes
  QuantumCircuit.noise = noise
  CompositeGate.noise = noise
  
  # Add to QASM header for parsing
  QuantumCircuit.header += "\ngate noise(m) a {}" + \
      "  // (local_qiskit_simulator) switch noise off (0) or on (1)"
  
subject: Fix typo in docstring of noise method (#366)