def __init__(self):
        self.packages = {}
        self.sheets = {}
Returns a ``SortedDict`` containing form fields for the given document.
dataset/ETHPy150Open VisTrails/VisTrails/vistrails/packages/spreadsheet/spreadsheet_registry.py/SpreadsheetRegistry.__init__--crossover with--dataset/ETHPy150Open benoitc/couchdbkit/couchdbkit/ext/django/forms.py/fields_for_document