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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def form(self):
 """ This attribute points to default form. If form was not selected manually then select the form which has the biggest number of input elements. The form value is just an `lxml.html` form element. Example:: g.go('some URL') # Choose form automatically print g.form # And now choose form manually g.choose_form(1) print g.form """


        if self._lxml_form is None:
            forms = [(idx, len(list(x.fields)))
                     for idx, x in enumerate(self.tree.forms)]
            if forms:
                idx = sorted(forms, key=lambda x: x[1], reverse=True)[0][0]
                self.choose_form(idx)
            else:
                raise DataNotFound('Response does not contains any form')
        return self._lxml_form