tlv: Fix from_dict() symmetry

the to_dict() method generates a {class_name: value} dictionary,
for both the nested and non-nested case.  However, before this patch,
the from_dict() method expects a plain list of child IE dicts
in the nested case.  This is illogical.

Let's make sure from_dict always expectes a {class_name: value} dict
for both nested and non-nested situations.

Change-Id: I07e4feb3800b420d8be7aae8911f828f1da9dab8
---
M pySim/tlv.py
1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/pySim/tlv.py b/pySim/tlv.py
index 6ea7dd1..4ac5ebf 100644
--- a/pySim/tlv.py
+++ b/pySim/tlv.py
@@ -157,13 +157,13 @@
     def from_dict(self, decoded: dict):
         """Set the IE internal decoded representation to data from the argument.
         If this is a nested IE, the child IE instance list is re-created."""
+        expected_key_name = camel_to_snake(type(self).__name__)
+        if not expected_key_name in decoded:
+            raise ValueError("Dict %s doesn't contain expected key %s" % (decoded, expected_key_name))
         if self.nested_collection:
-            self.children = self.nested_collection.from_dict(decoded)
+            self.children = self.nested_collection.from_dict(decoded[expected_key_name])
         else:
             self.children = []
-            expected_key_name = camel_to_snake(type(self).__name__)
-            if not expected_key_name in decoded:
-                raise ValueError("Dict %s doesn't contain expected key %s" % (decoded, expected_key_name))
             self.decoded = decoded[expected_key_name]
 
     def is_constructed(self):

