'Create a new `DefaultToolState` for this tool. It will be initialized
with default values for inputs. Grouping elements are filled in recursively.'

def initialize(self, trans, tool):

    self.inputs = {}
    context = ExpressionContext(self.inputs)
    for input in tool.inputs.itervalues():
        self.inputs[input.name] = input.get_initial_value(trans, context)
