[Minor] print_directory_tree returns a string

ghstack-source-id: d57f19dd8efcef06676fca40a4d6f95367ff1d55
Pull Request resolved: #1086

(cherry picked from commit 2b19ef1)

tensordict/utils.py

@@ -2138,7 +2138,7 @@ def _is_json_serializable(item):
     return isinstance(item, (str, int, float, bool)) or item is None
 
 
-def print_directory_tree(path, indent="", display_metadata=True):
+def print_directory_tree(path, indent="", display_metadata=True) -> str:
     """Prints the directory tree starting from the specified path.
 
     Args:
@@ -2147,7 +2147,11 @@ def print_directory_tree(path, indent="", display_metadata=True):
         display_metadata (bool): if ``True``, metadata of the dir will be
             displayed too.
 
+    Returns:
+        the string printed with the logger.
+
     """
+    string = []
     if display_metadata:
 
         def get_directory_size(path="."):
@@ -2169,17 +2173,23 @@ def format_size(size):
 
         total_size_bytes = get_directory_size(path)
         formatted_size = format_size(total_size_bytes)
-        logger.info(f"Directory size: {formatted_size}")
+        string.append(f"Directory size: {formatted_size}")
+        logger.info(string[-1])
 
     if os.path.isdir(path):
-        logger.info(indent + os.path.basename(path) + "/")
+        string.append(indent + os.path.basename(path) + "/")
+        logger.info(string[-1])
         indent += "    "
         for item in os.listdir(path):
-            print_directory_tree(
-                os.path.join(path, item), indent=indent, display_metadata=False
+            string.append(
+                print_directory_tree(
+                    os.path.join(path, item), indent=indent, display_metadata=False
+                )
             )
     else:
-        logger.info(indent + os.path.basename(path))
+        string.append(indent + os.path.basename(path))
+        logger.info(string[-1])
+    return "\n".join(string)
 
 
 def isin(