Added docs for Baggy.pickpairs

doc/Type/Baggy.pod

@@ -47,7 +47,25 @@ no effect on subsequent C<pick> invocations.
 
 =head2 method pickpairs
 
-=comment TODO
+Defined as:
+
+    multi method pickpairs(Baggy:D:) returns Pair:D
+    multi method pickpairs(Baggy:D: $count) returns List:D
+
+Returns a C<Pair> or a C<List> of C<Pair>s depending on the version of the method
+being invoked. Each C<Pair> returned has an element of the invocant as its key and the
+elements weight as its value. The elements are 'picked' without replacement. If C<*>
+is passed as C<$count>, or C<$count> is greater than or equal to the number of
+L<elements|#method elems> of the invocant, then all element/weight C<Pair>s from
+the invocant are returned in a random sequence.
+
+Note that each C<pickpairs> invocation maintains its own private state and has
+no effect on subsequent C<pickpairs> invocations.
+
+    my $breakfast = bag <eggs bacon bacon bacon>;
+    say $breakfast.pickpairs;                         # eggs => 1
+    say $breakfast.pickpairs(1);                      # (bacon => 3)
+    say $breakfast.pickpairs(*);                      # (eggs => 1 bacon => 3)
 
 =head2 method roll