Bring relative_child_offset typing in line with practice.

volatility/framework/objects/__init__.py

@@ -456,9 +456,9 @@ class Array(interfaces.objects.ObjectInterface, abc.Sequence):
         @classmethod
         def relative_child_offset(cls,
                                   template: interfaces.objects.Template,
-                                  child: interfaces.objects.Template) -> int:
+                                  child: str) -> int:
             """Returns the relative offset from the head of the parent data to the child member"""
-            if 'subtype' in template and child == 'subtype':
+            if 'subtype' in template.vol and child == 'subtype':
                 return 0
             raise IndexError("Member not present in array template: {}".format(child))
 
@@ -551,7 +551,7 @@ class Struct(interfaces.objects.ObjectInterface):
         @classmethod
         def relative_child_offset(cls,
                                   template: interfaces.objects.Template,
-                                  child: interfaces.objects.Template) -> int:
+                                  child: str) -> int:
             """Returns the relative offset of a child to its parent"""
             retlist = template.vol.members.get(child, None)
             if retlist is None:

volatility/framework/objects/templates.py

@@ -36,7 +36,7 @@ class ObjectTemplate(interfaces.objects.Template, validity.ValidityRoutines):
         """
         return self.vol.object_class.VolTemplateProxy.children(self)
 
-    def relative_child_offset(self, child: interfaces.objects.Template) -> int:
+    def relative_child_offset(self, child: str) -> int:
         """Returns the relative offset of a child of the templated object (see :class:`~volatility.framework.interfaces.objects.ObjectInterface.VolTemplateProxy`)
         """
         return self.vol.object_class.VolTemplateProxy.relative_child_offset(self, child)