code: def __getitem__(self, tf_name):
      if tf_name not in self.context:
          msg = "TF var {} not found in context {}"
          raise KeyError(msg.format(tf_name, self.name))
      return self.context[tf_name]
  
imports: from coremltools import _logger
  from coremltools.converters._profile_utils import _profile
  from coremltools.converters.mil._deployment_compatibility import AvailableTarget
  from coremltools.converters.mil.input_types import ImageType, InputType, RangeDim
  from coremltools.converters.mil.input_types import Shape
  from coremltools.converters.mil.input_types import TensorType, _get_shaping_class
  from coremltools.converters.mil.mil import Builder
  from coremltools.converters.mil.mil import Function, Program, get_new_symbol, types
  from coremltools.converters.mil.mil.types.symbolic import is_symbolic
  from coremltools.converters.mil.mil.var import Var
  from .._utils import get_output_names
  from .basic_graph_ops import simple_topsort
  from .convert_utils import convert_graph
label_desc: Use image node_id 8 for calling the TranscriptionContext obj's underlying member method code with example usage: obj.__getitem__(tf_name) and returns: self