'This method returns a string representation of the Form object.
Please note that if the form has radio/select/checkboxes the
first value will be put into the string representation and the
others will be lost.
:see: Unittest in test_form.py
:return: string representation of the Form object.'

def __str__(self):

    d = dict()
    d.update(self.items())
    for key in d:
        key_type = self.get_parameter_type(key, default=None)
        if (key_type in self.AVOID_STR_DUPLICATES):
            d[key] = d[key][:1]
    return urlencode(d, encoding=self.encoding, safe='')
