Grades the run's string input, output, and optional answer.
.. deprecated:: 0.5.0
StringEvaluator is deprecated. Use openevals instead: https://github.com/langchain-ai/openevals
StringEvaluator()The name evaluation, such as 'Accuracy' or 'Salience'.
The key in the run inputs to extract the input string.
The key in the run outputs to extra the prediction string.
The key in the example outputs the answer string.
Function that grades the run output against the example output.