code: def _unitary(norm):
      if norm not in (None, "ortho", "no_norm"):
          raise ValueError(
              f"Invalid value {norm} for norm, must be None, 'ortho' or 'no norm'"
          )
      return norm
  
imports: import numpy
  from pytensor.gradient import DisconnectedType
  from pytensor.graph.basic import Apply
  from pytensor.graph.op import Op
  from pytensor.tensor.basic import as_tensor_variable
  from pytensor.tensor.math import sqrt
  from pytensor.tensor.subtensor import set_subtensor
  from pytensor.tensor.type import TensorType, integer_dtypes
label_desc: Use image node_id 3 for calling a global function with example usage: _unitary(norm) and returns: norm