class_docstr: Represents the output of a supervised training or eval process.
class_docstr_tok: ["Represents","the","output","of","a","supervised","training","or","eval","process","."]
code: def _prefix_key(self, key, output_name):
      if key.find(output_name) != 0:
          key = output_name + self._SEPARATOR_CHAR + key
      return key
  
imports: import abc
  from tensorflow.python.framework import constant_op
  from tensorflow.python.framework import dtypes
  from tensorflow.python.framework import ops
  from tensorflow.python.framework import tensor
  from tensorflow.python.framework import tensor_util
  from tensorflow.python.keras.saving.utils_v1 import signature_def_utils
  from tensorflow.python.saved_model import signature_def_utils
label_desc: Use image node_id 3 for calling the _SupervisedOutput obj's underlying member method code with example usage: obj._prefix_key(key, output_name) and returns: key