def __init__(self, dict=None, preserve=1):
        """
        Create an empty dictionary, or update from 'dict'.
        """
        self.data = {}
        self.preserve=preserve
        if dict:
            self.update(dict)

        Create an empty dictionary, or update from 'dict'.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/python/util.py