There is no method named "register(fd, eventmask)"; fix markup to just indicate this is code.
diff --git a/Doc/library/select.rst b/Doc/library/select.rst
index 829b2a1..eb63710 100644
--- a/Doc/library/select.rst
+++ b/Doc/library/select.rst
@@ -233,7 +233,7 @@
.. method:: poll.modify(fd, eventmask)
Modifies an already registered fd. This has the same effect as
- :meth:`register(fd, eventmask)`. Attempting to modify a file descriptor
+ ``register(fd, eventmask)``. Attempting to modify a file descriptor
that was never registered causes an :exc:`IOError` exception with errno
:const:`ENOENT` to be raised.