bound value subtyping at AttMapEcho

attmap/attmap_echo.py

@@ -4,7 +4,13 @@
 from ._mixins import *
 
 
-class AttMapEcho(HomogeneousMixin, EchoMixin, AttMap):
+class AttMapEcho(EchoMixin, AttMap):
     """ An AttMap that returns key/attr if it has no set value. """
+
     def __contains__(self, item):
         return item in self.__dict__
+
+    @property
+    def _lower_type_bound(self):
+        """ Most specific type to which an inserted value may be converted """
+        return AttMapEcho