dalle add model parameter (#13201)

- **Description:** dalle_image_generator adding a new model parameter,
  - **Issue:** N/A,
  - **Dependencies:** 
  - **Tag maintainer: @hwchase17
  - **Twitter handle:**

---------

Co-authored-by: dafu <xiangbingze@wenru.wang>
Co-authored-by: Eugene Yurtsev <eyurtsev@gmail.com>
Co-authored-by: Erick Friis <erickfriis@gmail.com>

libs/langchain/langchain/utilities/dalle_image_generator.py

@@ -8,7 +8,10 @@ from langchain.utils import get_from_dict_or_env
 class DallEAPIWrapper(BaseModel):
     """Wrapper for OpenAI's DALL-E Image Generator.
 
+    https://platform.openai.com/docs/guides/images/generations?context=node
+
     Usage instructions:
+
     1. `pip install openai`
     2. save your OPENAI_API_KEY in an environment variable
     """
@@ -21,6 +24,8 @@ class DallEAPIWrapper(BaseModel):
     """Size of image to generate"""
     separator: str = "\n"
     """Separator to use when multiple URLs are returned."""
+    model: Optional[str] = None
+    """Model to use for image generation."""
 
     class Config:
         """Configuration for this pydantic object."""
@@ -47,6 +52,8 @@ class DallEAPIWrapper(BaseModel):
 
     def run(self, query: str) -> str:
         """Run query through OpenAI and parse result."""
-        response = self.client.create(prompt=query, n=self.n, size=self.size)
+        response = self.client.create(
+            prompt=query, n=self.n, size=self.size, model=self.model
+        )
         image_urls = self.separator.join([item["url"] for item in response["data"]])
         return image_urls if image_urls else "No image was generated"