langchain/document_loaders/blob_loaders/schema.py/Blob/as_string
class Blob:    def as_string(self) -> str:
        """Read data as a string."""
        if self.data is None and self.path:
            with open(str(self.path), "r", encoding=self.encoding) as f:
                return f.read()
        elif isinstance(self.data, bytes):
            return self.data.decode(self.encoding)
        elif isinstance(self.data, str):
            return self.data
        else:
            raise ValueError(f"Unable to get string for blob {self}")