community[minor]: Add solar model chat model (#18556)

Add our solar chat models, available model choices:
* solar-1-mini-chat
* solar-1-mini-translate-enko
* solar-1-mini-translate-koen

More documents and pricing can be found at
https://console.upstage.ai/services/solar.

The references to our solar model can be found at
* https://arxiv.org/abs/2402.17032

---------

Co-authored-by: Bagatur <22008038+baskaryan@users.noreply.github.com>
Co-authored-by: Bagatur <baskaryan@gmail.com>

libs/community/langchain_community/llms/solar.py

@@ -0,0 +1,119 @@
+from typing import Any, Dict, List, Optional
+
+import requests
+from langchain_core.callbacks import CallbackManagerForLLMRun
+from langchain_core.language_models import LLM
+from langchain_core.pydantic_v1 import BaseModel, Field, SecretStr, root_validator
+from langchain_core.utils import convert_to_secret_str, get_from_dict_or_env
+
+from langchain_community.llms.utils import enforce_stop_tokens
+
+SOLAR_SERVICE_URL_BASE = "https://api.upstage.ai/v1/solar"
+SOLAR_SERVICE = "https://api.upstage.ai"
+
+
+class _SolarClient(BaseModel):
+    """An API client that talks to the Solar server."""
+
+    api_key: SecretStr
+    """The API key to use for authentication."""
+    base_url: str = SOLAR_SERVICE_URL_BASE
+
+    def completion(self, request: Any) -> Any:
+        headers = {"Authorization": f"Bearer {self.api_key.get_secret_value()}"}
+        response = requests.post(
+            f"{self.base_url}/chat/completions",
+            headers=headers,
+            json=request,
+        )
+        if not response.ok:
+            raise ValueError(f"HTTP {response.status_code} error: {response.text}")
+        return response.json()["choices"][0]["message"]["content"]
+
+
+class SolarCommon(BaseModel):
+    _client: _SolarClient
+    base_url: str = SOLAR_SERVICE_URL_BASE
+    solar_api_key: Optional[SecretStr] = Field(default=None, alias="api_key")
+    """Solar API key. Get it here: https://console.upstage.ai/services/solar"""
+    model_name: str = Field(default="solar-1-mini-chat", alias="model")
+    """Model name. Available models listed here: https://console.upstage.ai/services/solar"""
+    max_tokens: int = Field(default=1024, alias="max context")
+    temperature = 0.3
+
+    class Config:
+        allow_population_by_field_name = True
+        arbitrary_types_allowed = True
+        extra = "ignore"
+
+    @property
+    def lc_secrets(self) -> dict:
+        return {"solar_api_key": "SOLAR_API_KEY"}
+
+    @property
+    def _default_params(self) -> Dict[str, Any]:
+        return {
+            "model": self.model_name,
+            "max_tokens": self.max_tokens,
+            "temperature": self.temperature,
+        }
+
+    @property
+    def _invocation_params(self) -> Dict[str, Any]:
+        return {**{"model": self.model_name}, **self._default_params}
+
+    @root_validator(pre=True)
+    def build_extra(cls, values: Dict[str, Any]) -> Dict[str, Any]:
+        return values
+
+    @root_validator()
+    def validate_environment(cls, values: Dict) -> Dict:
+        api_key = get_from_dict_or_env(values, "solar_api_key", "SOLAR_API_KEY")
+        if api_key is None or len(api_key) == 0:
+            raise ValueError("SOLAR_API_KEY must be configured")
+
+        values["solar_api_key"] = convert_to_secret_str(api_key)
+
+        if "base_url" not in values:
+            values["base_url"] = SOLAR_SERVICE_URL_BASE
+
+        if "base_url" in values and not values["base_url"].startswith(SOLAR_SERVICE):
+            raise ValueError("base_url must match with: " + SOLAR_SERVICE)
+
+        values["_client"] = _SolarClient(
+            api_key=values["solar_api_key"], base_url=values["base_url"]
+        )
+        return values
+
+    @property
+    def _llm_type(self) -> str:
+        return "solar"
+
+
+class Solar(SolarCommon, LLM):
+    """Solar large language models.
+    To use, you should have the environment variable
+    ``SOLAR_API_KEY`` set with your API key.
+    Referenced from https://console.upstage.ai/services/solar
+    """
+
+    class Config:
+        allow_population_by_field_name = True
+
+    def _call(
+        self,
+        prompt: str,
+        stop: Optional[List[str]] = None,
+        run_manager: Optional[CallbackManagerForLLMRun] = None,
+        **kwargs: Any,
+    ) -> str:
+        request = self._invocation_params
+        request["messages"] = [{"role": "user", "content": prompt}]
+        request.update(kwargs)
+        text = self._client.completion(request)
+        if stop is not None:
+            # This is required since the stop tokens
+            # are not enforced by the model parameters
+            text = enforce_stop_tokens(text, stop)
+
+        return text