code: def is_projector(operator):
      
      # verify that P^dag=P and P^2-P=0 holds up to relative numerical accuracy EPS.
      return (is_hermitian(operator) and (operator * operator - operator).norm(FROBENIUS)
              / operator.norm(FROBENIUS) < EPS)
docs: Check if operator is a projector.
  
      :param qutip.Qobj operator: The operator or matrix to be tested.
      :return: True if the operator is a projector.
      :rtype: bool