Make Block.insert_front accept iterables for multiple insertions

pystencils/astnodes.py

-import uuid
+import collections
 from typing import Any, List, Optional, Sequence, Set, Union
 
 import sympy as sp
@@ -279,8 +279,15 @@ class Block(Node):
             a.subs(subs_dict)
 
     def insert_front(self, node):
-        node.parent = self
-        self._nodes.insert(0, node)
+        if isinstance(node, collections.Iterable):
+            node = list(node)
+            for n in node:
+                n.parent = self
+
+            self._nodes = node + self._nodes
+        else:
+            node.parent = self
+            self._nodes.insert(0, node)
 
     def insert_before(self, new_node, insert_before):
         new_node.parent = self