core[patch]: remove requests (#19891)

Removes required usage of `requests` from `langchain-core`, all of which
has been deprecated.

- removes Tracer V1 implementations
- removes old `try_load_from_hub` github-based hub implementations

Removal done in a way where imports will still succeed, and usage will
fail with a `RuntimeError`.

libs/langchain/langchain/agents/loading.py

@@ -1,4 +1,5 @@
 """Functionality for loading agents."""
+
 import json
 import logging
 from pathlib import Path
@@ -8,7 +9,6 @@ import yaml
 from langchain_core._api import deprecated
 from langchain_core.language_models import BaseLanguageModel
 from langchain_core.tools import Tool
-from langchain_core.utils.loading import try_load_from_hub
 
 from langchain.agents.agent import BaseMultiActionAgent, BaseSingleActionAgent
 from langchain.agents.types import AGENT_TO_CLASS
@@ -100,13 +100,13 @@ def load_agent(
     Returns:
         An agent executor.
     """
-    valid_suffixes = {"json", "yaml"}
-    if hub_result := try_load_from_hub(
-        path, _load_agent_from_file, "agents", valid_suffixes
-    ):
-        return hub_result
-    else:
-        return _load_agent_from_file(path, **kwargs)
+    if isinstance(path, str) and path.startswith("lc://"):
+        raise RuntimeError(
+            "Loading from the deprecated github-based Hub is no longer supported. "
+            "Please use the new LangChain Hub at https://smith.langchain.com/hub "
+            "instead."
+        )
+    return _load_agent_from_file(path, **kwargs)
 
 
 def _load_agent_from_file(

libs/langchain/langchain/chains/loading.py

@@ -1,4 +1,5 @@
 """Functionality for loading chains."""
+
 import json
 from pathlib import Path
 from typing import Any, Union
@@ -10,7 +11,6 @@ from langchain_core.prompts.loading import (
     load_prompt,
     load_prompt_from_config,
 )
-from langchain_core.utils.loading import try_load_from_hub
 
 from langchain.chains import ReduceDocumentsChain
 from langchain.chains.api.base import APIChain
@@ -622,12 +622,13 @@ def load_chain_from_config(config: dict, **kwargs: Any) -> Chain:
 
 def load_chain(path: Union[str, Path], **kwargs: Any) -> Chain:
     """Unified method for loading a chain from LangChainHub or local fs."""
-    if hub_result := try_load_from_hub(
-        path, _load_chain_from_file, "chains", {"json", "yaml"}, **kwargs
-    ):
-        return hub_result
-    else:
-        return _load_chain_from_file(path, **kwargs)
+    if isinstance(path, str) and path.startswith("lc://"):
+        raise RuntimeError(
+            "Loading from the deprecated github-based Hub is no longer supported. "
+            "Please use the new LangChain Hub at https://smith.langchain.com/hub "
+            "instead."
+        )
+    return _load_chain_from_file(path, **kwargs)
 
 
 def _load_chain_from_file(file: Union[str, Path], **kwargs: Any) -> Chain: