docs/pyb.Pin: af_list() is a normal method, not a class method.

docs/library/pyb.Pin.rst

@@ -85,11 +85,7 @@ Constructors
 
     Class methods
     -------------
-    
-    .. method:: Pin.af_list()
-    
-       Returns an array of alternate functions available for this pin.
-    
+
     .. method:: Pin.debug([state])
     
        Get or set the debugging state (``True`` or ``False`` for on or off).
@@ -179,6 +175,10 @@ Methods
     
        Get the pin port.
     
+    .. method:: Pin.af_list()
+
+       Returns an array of alternate functions available for this pin.
+
 .. method:: pin.pull()
 
     Returns the currently configured pull of the pin. The integer returned