Given a target dct and a dict of {key:default value} pairs,
    calls setdefault for all of those pairs.

def setdefaults(dct, defaults):
    """Given a target dct and a dict of {key:default value} pairs,
    calls setdefault for all of those pairs."""
    for key in defaults:
        dct.setdefault(key, defaults[key])

    return dct