code: def choose_form(self, number=None, xpath=None, name=None, **kwargs):
          
  
          id_ = kwargs.pop('id', None)
          if id_ is not None:
              try:
                  self._lxml_form = self.select('//form[@id="%s"]' % id_).node()
              except IndexError:
                  raise DataNotFound("There is no form with id: %s" % id_)
          elif name is not None:
              try:
                  self._lxml_form = self.select(
                      '//form[@name="%s"]' % name).node()
              except IndexError:
                  raise DataNotFound('There is no form with name: %s' % name)
          elif number is not None:
              try:
                  self._lxml_form = self.tree.forms[number]
              except IndexError:
                  raise DataNotFound('There is no form with number: %s' % number)
          elif xpath is not None:
              try:
                  self._lxml_form = self.select(xpath).node()
              except IndexError:
                  raise DataNotFound(
                      'Could not find form with xpath: %s' % xpath)
          else:
              raise GrabMisuseError('choose_form methods requires one of '
                                    '[number, id, name, xpath] arguments')
docs: Set the default form.
  
          :param number: number of form (starting from zero)
          :param id: value of "id" attribute
          :param name: value of "name" attribute
          :param xpath: XPath query
          :raises: :class:`DataNotFound` if form not found
          :raises: :class:`GrabMisuseError`
              if method is called without parameters
  
          Selected form will be available via `form` attribute of `Grab`
          instance. All form methods will work with default form.
  
          Examples::
  
              # Select second form
              g.choose_form(1)
  
              # Select by id
              g.choose_form(id="register")
  
              # Select by name
              g.choose_form(name="signup")
  
              # Select by xpath
              g.choose_form(xpath='//form[contains(@action, "/submit")]')