[DICT] Add Python support for update

[EmilyBourne]

Describe the feature

Syntactic and semantic support should be added for update. This should be tested by implementing Python printing

Test Code

Provide code which does not currently work but which should do when this issue is fixed:

def foo():
    a = {1:1.0, 2:2.0}
    b = {3:3.0, 1:4.0}
    a.update(b)
    return a, b