Refactoring merge-dict-assign does not trigger when the value being set is a function parameter

[ruancomelli]

Checklist

• I have searched the Sourcery documentation for the issue, and found nothing
• I have checked there are no open bugs referencing the same bug or problem

Description

Related to #339 (comment).

Code snippet that reproduces issue

1 - Case reported in #339

Input:

def __init__(self, toUserName, fromUserName, mediaId):
    self.__dict = {}
    self.__dict['ToUserName'] = toUserName
    self.__dict['FromUserName'] = fromUserName
    self.__dict["CreateTime"] = int(time.time())
    self.__dict["MediaId"] = mediaId

Expected refactored code:

def __init__(self, toUserName, fromUserName, mediaId):
    self.__dict = {
        'ToUserName': toUserName,
        'FromUserName': fromUserName,
        "CreateTime": int(time.time()),
        "MediaId": mediaId
    }

Actual refactored code:

def __init__(self, toUserName, fromUserName, mediaId):
    self.__dict = {
        'ToUserName': toUserName,
        'FromUserName': fromUserName,
        "CreateTime": int(time.time()),
    }
    self.__dict["MediaId"] = mediaId

2 - Simplified version

The bug can more easily be reproduced with the following snippets:
Input:

def foo(mediaId):
    d = {}
    d["CreateTime"] = int(time.time())
    d["MediaId"] = mediaId

Expected refactored code:

def foo(mediaId):
    d = {"CreateTime": int(time.time()), "MediaId": mediaId}

Actual refactored code:

def foo(mediaId):
    d = {"CreateTime": int(time.time())}
    d["MediaId"] = mediaId

Debug Information

Sourcery Version: 1.2.0

[ruancomelli]

Relabeled this as an enhancement proposal since the refactoring is still correct.
We definitely want Sourcery to keep on refactoring until all items are added to the dictionary instantiation, but this is not a bug.