Update EIP-7495: Remove redundant is_active_field helper

EIPS/eip-7495.md

@@ -75,12 +75,9 @@ Serialization of `StableContainer[N]` is defined similarly to the [existing logi
 - If variable-length fields are serialized, their offsets are relative to the start of serialized active fields, after the `Bitvector[N]`
 
 ```python
-def is_active_field(element):
-    return not is_optional(element) or element is not None
-
 # Determine active fields
-active_fields = Bitvector[N](([is_active_field(element) for element in value] + [False] * N)[:N])
-active_values = [element for element in value if is_active_field(element)]
+active_fields = Bitvector[N](([element is not None for element in value] + [False] * N)[:N])
+active_values = [element for element in value if element is not None]
 
 # Recursively serialize
 fixed_parts = [serialize(element) if not is_variable_size(element) else None for element in active_values]
@@ -120,7 +117,7 @@ To merkleize a `StableContainer[N]`, a `Bitvector[N]` is constructed, indicating
 
 Merkleization `hash_tree_root(value)` of an object `value` is extended with:
 
-- `mix_in_aux(merkleize(([hash_tree_root(element) if is_active_field(element) else Bytes32() for element in value.data] + [Bytes32()] * N)[:N]), hash_tree_root(value.active_fields))` if `value` is a `StableContainer[N]`.
+- `mix_in_aux(merkleize(([hash_tree_root(element) if element is not None else Bytes32() for element in value.data] + [Bytes32()] * N)[:N]), hash_tree_root(value.active_fields))` if `value` is a `StableContainer[N]`.
 
 ### `Profile[B]`