Adds sum, refs #1494

doc/Type/Any.pod6

@@ -1304,6 +1304,21 @@ one has size 2 (because partials are allowed), and an overlap of 2 also.
 Please see also L<C<list.rotor>|/type/List#method_rotor> for examples applied to
 lists.
 
+=head2 method sum
+
+Defined as:
+
+    method sum() is nodal
+
+If the content is iterable, it returns the sum of the values after pulling them
+one by one.
+
+=for code
+(3,2,1).sum; # OUTPUT: «6␤»
+say 3.sum;   # OUTPUT: «3␤»
+
+It will fail if any of the elements cannot be converted to a number.
+
 =end pod
 
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