code: def get_basis(expr, *, basis=None, replace_none=True, **options):
      """
      Returns a basis state instance corresponding to the basis specified in
      options=s. If no basis is specified, the function tries to form a default
      basis state of the given expression.
  
      There are three behaviors:
  
      1. The basis specified in options is already an instance of StateBase. If
         this is the case, it is simply returned. If the class is specified but
         not an instance, a default instance is returned.
  
      2. The basis specified is an operator or set of operators. If this
         is the case, the operator_to_state mapping method is used.
  
      3. No basis is specified. If expr is a state, then a default instance of
         its class is returned.  If expr is an operator, then it is mapped to the
         corresponding state.  If it is neither, then we cannot obtain the basis
         state.
  
      If the basis cannot be mapped, then it is not changed.
  
      This will be called from within represent, and represent will
      only pass QExpr's.
  
      TODO (?): Support for Muls and other types of expressions?
  
      Parameters
      ==========
  
      expr : Operator or StateBase
          Expression whose basis is sought
  
      Examples
      ========
  
      >>> from sympy.physics.quantum.represent import get_basis
      >>> from sympy.physics.quantum.cartesian import XOp, XKet, PxOp, PxKet
      >>> x = XKet()
      >>> X = XOp()
      >>> get_basis(x)
      |x>
      >>> get_basis(X)
      |x>
      >>> get_basis(x, basis=PxOp())
      |px>
      >>> get_basis(x, basis=PxKet)
      |px>
  
      """
  
      if basis is None and not replace_none:
          return None
  
      if basis is None:
          if isinstance(expr, KetBase):
              return _make_default(expr.__class__)
          elif isinstance(expr, BraBase):
              return _make_default(expr.dual_class())
          elif isinstance(expr, Operator):
              state_inst = operators_to_state(expr)
              return state_inst if state_inst is not None else None
          else:
              return None
      elif isinstance(basis, Operator) or (
          not isinstance(basis, StateBase)
          and issubclass(basis, Operator)
      ):
          state = operators_to_state(basis)
          if state is None:
              return None
          elif isinstance(state, StateBase):
              return state
          else:
              return _make_default(state)
      elif isinstance(basis, StateBase):
          return basis
      elif issubclass(basis, StateBase):
          return _make_default(basis)
      else:
          return None
  
imports: from sympy.core.add import Add
  from sympy.core.expr import Expr
  from sympy.core.mul import Mul
  from sympy.core.numbers import I
  from sympy.core.power import Pow
  from sympy.integrals.integrals import integrate
  from sympy.physics.quantum.dagger import Dagger
  from sympy.physics.quantum.commutator import Commutator
  from sympy.physics.quantum.anticommutator import AntiCommutator
  from sympy.physics.quantum.innerproduct import InnerProduct
  from sympy.physics.quantum.qexpr import QExpr
  from sympy.physics.quantum.tensorproduct import TensorProduct
  from sympy.physics.quantum.matrixutils import flatten_scalar
  from sympy.physics.quantum.state import KetBase, BraBase, StateBase
  from sympy.physics.quantum.operator import Operator, OuterProduct
  from sympy.physics.quantum.qapply import qapply
  from sympy.physics.quantum.operatorset import operators_to_state, state_to_operators
label_desc: Use image node_id 6 for calling a global function with example usage: get_basis(expr) and returns: None, _make_default, _make_default, None, basis, unknown, None, state, _make_default, _make_default, None