Fix issue with negative prompts and allow model_name argument (#63)

* Add option to change model name and fix negative prompt bugs

diffusion/inference/inference_model.py

@@ -35,10 +35,14 @@ class StableDiffusionInference():
             Default: ``None``.
     """
 
-    def __init__(self, pretrained: bool = False, prediction_type: str = 'epsilon'):
+    def __init__(self,
+                 model_name: str = 'stabilityai/stable-diffusion-2-base',
+                 pretrained: bool = False,
+                 prediction_type: str = 'epsilon'):
         self.device = torch.cuda.current_device()
 
         model = stable_diffusion_2(
+            model_name=model_name,
             pretrained=pretrained,
             prediction_type=prediction_type,
             encode_latents_in_fp16=True,
@@ -68,12 +72,14 @@ def predict(self, model_requests: List[Dict[str, Any]]):
             # Prompts and negative prompts if available
             if isinstance(inputs, str):
                 prompts.append(inputs)
-            elif isinstance(input, Dict):
-                if 'prompt' not in req:
+            elif isinstance(inputs, Dict):
+                if 'prompt' not in inputs:
                     raise RuntimeError('"prompt" must be provided to generate call if using a dict as input')
                 prompts.append(inputs['prompt'])
-                if 'negative_prompt' in req:
+                if 'negative_prompt' in inputs:
                     negative_prompts.append(inputs['negative_prompt'])
+            else:
+                raise RuntimeError(f'Input must be of type string or dict, but it is type: {type(inputs)}')
 
             generate_kwargs = req['parameters']