A bug with add_trait ? -> is there a need to call a "register" function after adding a trait ?

add_trait_bug.py

#!/usr/bin/python
# -*- coding: utf-8 -*-
""" A bug with add_trait ?
-> is there a need to call a "register" function after adding a trait ?

Documentation reference for `add_trait` :
http://docs.enthought.com/traits/traits_user_manual/advanced.html#per-object-trait-attributes

Pierre Haessig — October 2013
"""

import traits
from traits.api import HasTraits, Float

print(traits.__version__)
# -> 4.3.0

class A(HasTraits):
    param1 = Float(1)

a = A()
print(a.get())
# -> {'param1': 1}

# Add a trait
a.add_trait('param2', Float(2))
print(a.get())
# -> {'param1': 1}
#     -> 'param2' is missing !

# Visit the trait:
a.param2
# Now param2 is visible
print(a.get())
# -> {'param2': 2, 'param1': 1}