code: def _as_scalar(res, dtype=None):
      """Return ``None`` or a `TensorVariable` of float type"""
      if dtype is None:
          dtype = config.floatX
      if all(s == 1 for s in res.type.shape):
          while res.owner and isinstance(res.owner.op, DimShuffle):
              res = res.owner.inputs[0]
          # may still have some number of True's
          if res.type.ndim > 0:
              rval = res.dimshuffle()
          else:
              rval = res
          if rval.type.dtype in integer_dtypes:
              # We check that the upcast of res and dtype won't change dtype.
              # If dtype is float64, we will cast int64 to float64.
              # This is valid when res is a scalar used as input to a dot22
              # as the cast of the scalar can be done before or after the dot22
              # and this will give the same result.
              if pytensor.scalar.upcast(res.dtype, dtype) == dtype:
                  return ptb.cast(rval, dtype)
              else:
                  return None
  
          return rval
  
imports: import copy
  import logging
  import time
  import numpy
  from pytensor.tensor.rewriting.basic import register_specialize
  import pytensor.scalar
  from pytensor.compile.mode import optdb
  from pytensor.configdefaults import config
  from pytensor.graph.features import ReplacementDidNotRemoveError, ReplaceValidate
  from pytensor.graph.rewriting.basic import EquilibriumGraphRewriter, GraphRewriter, copy_stack_trace, in2out, node_rewriter
  from pytensor.graph.rewriting.db import SequenceDB
  from pytensor.graph.utils import InconsistencyError
  from pytensor.tensor import basic
  from pytensor.tensor.blas import Dot22, _dot22, _dot22scalar, batched_dot, gemm_inplace, gemm_no_inplace, gemv_inplace, gemv_no_inplace, ger, ger_destructive
  from pytensor.tensor.elemwise import DimShuffle, Elemwise
  from pytensor.tensor.exceptions import NotScalarConstantError
  from pytensor.tensor.math import Dot, _matrix_matrix_matmul, add, mul, neg, sub
  from pytensor.tensor.rewriting.elemwise import local_dimshuffle_lift
  from pytensor.tensor.type import DenseTensorType, TensorType, integer_dtypes, values_eq_approx_remove_inf_nan
label_desc: Use image node_id 2 for calling a global function with example usage: _as_scalar(res, dtype) and returns: rval, ptb, None