Support combining multiple output parsers

[jmandel]

Not sure if this is a recommended approach, but I'm finding in my prompts that I want to cause outputs like:

{
  "system": "http://www.nlm.nih.gov/research/umls/rxnorm",
  "display": "hydroxychloroquine",
  "code": "5521",
}

New Query: ?system=loinc&display=medication
  
Final Grade: A

Justification: The code "5521" for "hydroxychloroquine" is the most appropriate code for the medication
mentioned in the clinical note. It is a valid RXNORM code and accurately represents the medication mentioned.

It's easier for me to create a JSONOutputParser and combined it with a couple of RegexOutpuParsers,and the logic for this combination can be abstracted into something like this "Combining" output parser.

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[nfcampos]

@jmandel thanks for this, could you provide an example of this in action?

[jmandel]

@nfcampos sure thing -- here's how I'm using it currently, to parse output like in the example above:

const chain = new LLMChain({
  outputParser: new MultiOutputParser(
    new CodingsParser("codings"), // parses all JSON objects in output --> `Record<string, any>[]`
    new RegexParser(/Final Grade: (A|B|C)/i, ["grade"], "noGrade"),
    new RegexParser(/Justification: (.*)/i, ["rationale"], "noRationale"),
    new RegexParser(
      /New Query: \?system=(\S+)&display=(\S+)/i,
      ["newQuerySystem", "newQuery"],
      "noQuery"
    )
  ),
  prompt,
  llm
});

[hwchase17]

oh this is pretty cool. i like this a lot - i can do something similar in the python version, and then we can release at the same time and make a cool announcement

i think all thats missing from this PR is an example to put in the docs

[jmandel]

Added an example and updated the class name.