community[patch]: import flattening fix (#20110)

This PR should make it easier for linters to do type checking and for IDEs to jump to definition of code.

See #20050 as a template for this PR.
- As a byproduct: Added 3 missed `test_imports`.
- Added missed `SolarChat` in to __init___.py Added it into test_import
ut.
- Added `# type: ignore` to fix linting. It is not clear, why linting
errors appear after ^ changes.

---------

Co-authored-by: Eugene Yurtsev <eyurtsev@gmail.com>

libs/community/langchain_community/document_transformers/__init__.py

@@ -16,7 +16,56 @@
 """  # noqa: E501
 
 import importlib
-from typing import Any
+from typing import TYPE_CHECKING, Any
+
+if TYPE_CHECKING:
+    from langchain_community.document_transformers.beautiful_soup_transformer import (
+        BeautifulSoupTransformer,  # noqa: F401
+    )
+    from langchain_community.document_transformers.doctran_text_extract import (
+        DoctranPropertyExtractor,  # noqa: F401
+    )
+    from langchain_community.document_transformers.doctran_text_qa import (
+        DoctranQATransformer,  # noqa: F401
+    )
+    from langchain_community.document_transformers.doctran_text_translate import (
+        DoctranTextTranslator,  # noqa: F401
+    )
+    from langchain_community.document_transformers.embeddings_redundant_filter import (
+        EmbeddingsClusteringFilter,  # noqa: F401
+        EmbeddingsRedundantFilter,  # noqa: F401
+        get_stateful_documents,  # noqa: F401
+    )
+    from langchain_community.document_transformers.google_translate import (
+        GoogleTranslateTransformer,  # noqa: F401
+    )
+    from langchain_community.document_transformers.html2text import (
+        Html2TextTransformer,  # noqa: F401
+    )
+    from langchain_community.document_transformers.long_context_reorder import (
+        LongContextReorder,  # noqa: F401
+    )
+    from langchain_community.document_transformers.nuclia_text_transform import (
+        NucliaTextTransformer,  # noqa: F401
+    )
+    from langchain_community.document_transformers.openai_functions import (
+        OpenAIMetadataTagger,  # noqa: F401
+    )
+
+__all__ = [
+    "BeautifulSoupTransformer",
+    "DoctranPropertyExtractor",
+    "DoctranQATransformer",
+    "DoctranTextTranslator",
+    "EmbeddingsClusteringFilter",
+    "EmbeddingsRedundantFilter",
+    "GoogleTranslateTransformer",
+    "Html2TextTransformer",
+    "LongContextReorder",
+    "NucliaTextTransformer",
+    "OpenAIMetadataTagger",
+    "get_stateful_documents",
+]
 
 _module_lookup = {
     "BeautifulSoupTransformer": "langchain_community.document_transformers.beautiful_soup_transformer",  # noqa: E501