fix: gas estimation with new lll shape

vyper/compiler/utils.py

@@ -9,10 +9,11 @@ def build_gas_estimates(lll_nodes: LLLnode) -> dict:
         if len(lll_nodes.args) > 0 and lll_nodes.args[-1].value == "return":
             lll_nodes = lll_nodes.args[-1].args[1].args[0]
 
-    assert lll_nodes.value == "seq"
-    for arg in lll_nodes.args:
-        if arg.func_name is not None:
-            gas_estimates[arg.func_name] = arg.total_gas
+    external_sub = next((i for i in lll_nodes.args if i.value == "with"), None)
+    if external_sub:
+        for func_lll in external_sub.args[-1].args:
+            if func_lll.func_name is not None:
+                gas_estimates[func_lll.func_name] = func_lll.total_gas
 
     return gas_estimates