Litellm router code coverage 3 (#6274)

* refactor(router.py): move assistants api endpoints to using 1 pass-through factory function

Reduces code, increases testing coverage

* refactor(router.py): reduce _common_check_available_deployment function size

make code more maintainable - reduce possible errors

* test(router_code_coverage.py): include batch_utils + pattern matching in enforced 100% code coverage

Improves reliability

* fix(router.py): fix model id match model dump

tests/router_unit_tests/test_router_batch_utils.py

@@ -0,0 +1,84 @@
+import sys
+import os
+import traceback
+from dotenv import load_dotenv
+from fastapi import Request
+from datetime import datetime
+
+sys.path.insert(
+    0, os.path.abspath("../..")
+)  # Adds the parent directory to the system path
+from litellm import Router
+import pytest
+import litellm
+from unittest.mock import patch, MagicMock, AsyncMock
+
+import json
+from io import BytesIO
+from typing import Dict, List
+from litellm.router_utils.batch_utils import (
+    replace_model_in_jsonl,
+    _get_router_metadata_variable_name,
+)
+
+
+# Fixtures
+@pytest.fixture
+def sample_jsonl_data() -> List[Dict]:
+    """Fixture providing sample JSONL data"""
+    return [
+        {
+            "body": {
+                "model": "gpt-3.5-turbo",
+                "messages": [{"role": "user", "content": "Hello"}],
+            }
+        },
+        {"body": {"model": "gpt-4", "messages": [{"role": "user", "content": "Hi"}]}},
+    ]
+
+
+@pytest.fixture
+def sample_jsonl_bytes(sample_jsonl_data) -> bytes:
+    """Fixture providing sample JSONL as bytes"""
+    jsonl_str = "\n".join(json.dumps(line) for line in sample_jsonl_data)
+    return jsonl_str.encode("utf-8")
+
+
+@pytest.fixture
+def sample_file_like(sample_jsonl_bytes):
+    """Fixture providing a file-like object"""
+    return BytesIO(sample_jsonl_bytes)
+
+
+# Test cases
+def test_bytes_input(sample_jsonl_bytes):
+    """Test with bytes input"""
+    new_model = "claude-3"
+    result = replace_model_in_jsonl(sample_jsonl_bytes, new_model)
+
+    assert result is not None
+
+
+def test_tuple_input(sample_jsonl_bytes):
+    """Test with tuple input"""
+    new_model = "claude-3"
+    test_tuple = ("test.jsonl", sample_jsonl_bytes, "application/json")
+    result = replace_model_in_jsonl(test_tuple, new_model)
+
+    assert result is not None
+
+
+def test_file_like_object(sample_file_like):
+    """Test with file-like object input"""
+    new_model = "claude-3"
+    result = replace_model_in_jsonl(sample_file_like, new_model)
+
+    assert result is not None
+
+
+def test_router_metadata_variable_name():
+    """Test that the variable name is correct"""
+    assert _get_router_metadata_variable_name(function_name="completion") == "metadata"
+    assert (
+        _get_router_metadata_variable_name(function_name="batch") == "litellm_metadata"
+    )