Added docs for Baggy.pick

Author: Jan-Olof Hendig

doc/Type/Baggy.pod

@@ -21,7 +21,29 @@ L<Mixy>.
 
 =head2 method pick
 
-=comment TODO
+Defined as:
+
+    multi method pick(Baggy:D:) returns Any
+    multi method pick(Baggy:D: $count) returns Seq:D
+
+Like an ordinary list L<pick|/type/List#routine_pick>, but returns keys
+of the invocant weighted by their values, as if the keys were replicated
+the number of times indicated by the corresponding value and then list
+pick used. The underlying metaphor for picking is that you're pulling
+colored marbles out a bag. (For "picking with replacement" see
+L<roll|#method roll> instead). If C<*> is passed as C<$count>, or C<$count> is
+greater than or equal to the L<total|#method total> of the invocant, then
+C<total> elements from the invocant are returned in a random sequence.
+
+Note that each C<pick> invocation maintains its own private state and has
+no effect on subsequent C<pick> invocations.
+
+    my $breakfast = bag <eggs bacon bacon bacon>;
+    say $breakfast.pick;                              # eggs
+    say $breakfast.pick(2);                           # (eggs bacon)
+
+    say $breakfast.total;                             # 4
+    say $breakfast.pick(*);                           # (bacon bacon bacon eggs)
 
 =head2 method pickpairs