def __init__(self, key, operator=None, required=True, scope=None, iterate=False):
self.key = key<EOL>self.operator = operator<EOL>self.required = required<EOL>self.scope = scope<EOL>self.iterate = iterate<EOL>
Only `key` is required

Arguments:
operator (str)     -- "?" optional,  "!" for complete arrays; defaults to None (i.e. required)
required (boolean) -- whether the key is required in the output (defaults to True)
scope (`Selector`) -- restrict extraction to elements matching this selector
iterate (boolean)  -- whether multiple objects will be extracted (defaults to False)