Source code for langchain.output_parsers.yaml
import json
import re
from typing import Type, TypeVar
import yaml
from langchain_core.exceptions import OutputParserException
from langchain_core.output_parsers import BaseOutputParser
from langchain_core.pydantic_v1 import BaseModel, ValidationError
from langchain.output_parsers.format_instructions import YAML_FORMAT_INSTRUCTIONS
T = TypeVar("T", bound=BaseModel)
[docs]class YamlOutputParser(BaseOutputParser[T]):
    """Parse YAML output using a pydantic model."""
    pydantic_object: Type[T]
    """The pydantic model to parse."""
    pattern: re.Pattern = re.compile(
        r"^```(?:ya?ml)?(?P<yaml>[^`]*)", re.MULTILINE | re.DOTALL
    )
    """Regex pattern to match yaml code blocks 
    within triple backticks with optional yaml or yml prefix."""
[docs]    def parse(self, text: str) -> T:
        try:
            # Greedy search for 1st yaml candidate.
            match = re.search(self.pattern, text.strip())
            yaml_str = ""
            if match:
                yaml_str = match.group("yaml")
            json_object = yaml.safe_load(yaml_str)
            return self.pydantic_object.parse_obj(json_object)
        except (yaml.YAMLError, ValidationError) as e:
            name = self.pydantic_object.__name__
            msg = f"Failed to parse {name} from completion {text}. Got: {e}"
            raise OutputParserException(msg, llm_output=text)
[docs]    def get_format_instructions(self) -> str:
        schema = self.pydantic_object.schema()
        # Remove extraneous fields.
        reduced_schema = schema