Add stability ai image model

CONTRIBUTING.md

@@ -143,3 +143,37 @@ If you discover a potential security issue in this project we ask that you notif
 ## Licensing
 
 See the [LICENSE](./LICENSE) file for our project's licensing. We will ask you to confirm the licensing of your contribution.
+
+## Stability Specific Instructions 
+
+* Modified files 
+
+   1. src/strands/event_loop/streaming.py
+   2. tests/strands/event_loop/test_streaming.py
+
+   These files have fixes to make the image return to agent consumers work.
+
+* New Files 
+	1. src/strands/models/_stabilityaiclient.py - A class with a rest client implementation for Stability
+	2. src/strands/models/stability.py - The main model provider implementation
+	3. tests-integ/test_model_stability.py - Integration test to test the image generation workflow.
+	4. tests/TODO.lis - A text file containing TODOs.
+	5. tests/strands/models/test_stability.py - Unit tests for the model provider
+
+
+* Running the stability tests and testing the code 
+
+You can run the integration test for the stability model as follows 
+```
+   cd path/to/strands-agents-sdk-python
+   export STABILITY_API_KEY=<your api key>
+   hatch test tests-integ/test_model_stability.py 
+```
+
+You can also install this as a editable module in a python project and write a agent 
+
+```
+pip install -e /path/to/strands-agents-sdk-python
+Sample code similar to
+https://gist.github.com/sayanc82/17f0d2442acd78f74f8393f58b552c54
+```

TODO.lis

@@ -0,0 +1,4 @@
+Add support for all the parameters for core and 3.5 
+Do specific config validation for the 3 models, support parameters like cfg for sd3.5
+Cleanup code :- Modularize. Move validation to its own methods for example. 
+Add documentation similar to other model providers

pyproject.toml

@@ -54,10 +54,12 @@ dev = [
     "hatch>=1.0.0,<2.0.0",
     "moto>=5.1.0,<6.0.0",
     "mypy>=1.15.0,<2.0.0",
+    "Pillow>=11.0",
     "pre-commit>=3.2.0,<4.2.0",
     "pytest>=8.0.0,<9.0.0",
     "pytest-asyncio>=0.26.0,<0.27.0",
     "ruff>=0.4.4,<0.5.0",
+    "types-Pillow>=10.2.0.20240822",
 ]
 docs = [
     "sphinx>=5.0.0,<6.0.0",
@@ -119,6 +121,7 @@ lint-fix = [
 features = ["anthropic", "litellm", "llamaapi", "ollama", "openai", "otel"]
 extra-dependencies = [
     "moto>=5.1.0,<6.0.0",
+    "Pillow>=11.0",
     "pytest>=8.0.0,<9.0.0",
     "pytest-asyncio>=0.26.0,<0.27.0",
     "pytest-cov>=4.1.0,<5.0.0",
@@ -220,6 +223,10 @@ ignore_missing_imports = false
 module = "litellm"
 ignore_missing_imports = true
 
+[[tool.mypy.overrides]]
+module = "PIL"
+ignore_missing_imports = true
+
 [tool.ruff]
 line-length = 120
 include = ["examples/**/*.py", "src/**/*.py", "tests/**/*.py", "tests-integ/**/*.py"]

src/strands/event_loop/streaming.py

@@ -102,13 +102,14 @@ def handle_content_block_start(event: ContentBlockStartEvent) -> dict[str, Any]:
 
 
 def handle_content_block_delta(
-    event: ContentBlockDeltaEvent, state: dict[str, Any]
+    event: ContentBlockDeltaEvent, state: dict[str, Any], **kwargs: Any
 ) -> tuple[dict[str, Any], dict[str, Any]]:
     """Handles content block delta updates by appending text, tool input, or reasoning content to the state.
 
     Args:
         event: Delta event.
         state: The current state of message processing.
+        **kwargs: Additional keyword arguments to pass to the callback handler.
 
     Returns:
         Updated state with appended text or tool input.
@@ -150,7 +151,11 @@ def handle_content_block_delta(
                 "delta": delta_content,
                 "reasoning": True,
             }
-
+    elif "image" in delta_content:
+        # Handle the new ImageContent structure
+        image_content = delta_content["image"]
+        state["image"] = image_content
+        callback_event["callback"] = {"image": image_content, "delta": delta_content, **kwargs}
     return state, callback_event
 
 
@@ -168,7 +173,7 @@ def handle_content_block_stop(state: dict[str, Any]) -> dict[str, Any]:
     current_tool_use = state["current_tool_use"]
     text = state["text"]
     reasoning_text = state["reasoningText"]
-
+    image = state["image"]
     if current_tool_use:
         if "input" not in current_tool_use:
             current_tool_use["input"] = ""
@@ -192,7 +197,6 @@ def handle_content_block_stop(state: dict[str, Any]) -> dict[str, Any]:
     elif text:
         content.append({"text": text})
         state["text"] = ""
-
     elif reasoning_text:
         content.append(
             {
@@ -205,6 +209,9 @@ def handle_content_block_stop(state: dict[str, Any]) -> dict[str, Any]:
             }
         )
         state["reasoningText"] = ""
+    elif image:
+        content.append({"image": image})
+        state["image"] = ""
 
     return state
 
@@ -272,6 +279,7 @@ def process_stream(
         "current_tool_use": {},
         "reasoningText": "",
         "signature": "",
+        "image": None,
     }
     state["content"] = state["message"]["content"]