Don't use instances of complex types as a default value in args

This can produce unexpected buthurt (at least for me).
Cause python has super strange behavior in this case.

E.g.

def a(t=[]):
    t.append(1)
    print(t)

a() # prints [1]
a() # prints [1, 1]

Change-Id: Ie5287dd4c958d2d1ccaf98486b9522a2d2c18724
Merge "Don't use instances of complex types as a default value in args"