Add start_token parameter to prediction function

Closes #40 (closed)

dan/predict/prediction.py

@@ -92,6 +92,7 @@ class DAN:
         input_sizes,
         confidences=False,
         attentions=False,
+        start_token=None,
     ):
         """
         Run prediction on an input image.
@@ -102,7 +103,9 @@ class DAN:
         """
         input_tensor = input_tensor.to(self.device)
 
-        start_token = len(self.charset) + 1
+        start_token = (
+            self.charset.index(start_token) if start_token else len(self.charset) + 1
+        )
         end_token = len(self.charset)
 
         # Run the prediction.