'A :class:`~urllib3.fields.RequestField` factory from old-style tuple parameters.
Supports constructing :class:`~urllib3.fields.RequestField` from parameter
of key/value strings AND key/filetuple. A filetuple is a (filename, data, MIME type)
tuple where the MIME type is optional. For example: ::
\'foo\': \'bar\',
\'fakefile\': (\'foofile.txt\', \'contents of foofile\'),
\'realfile\': (\'barfile.txt\', open(\'realfile\').read()),
\'typedfile\': (\'bazfile.bin\', open(\'bazfile\').read(), \'image/jpeg\'),
\'nonamefile\': \'contents of nonamefile field\',
Field names and filenames must be unicode.'

@classmethod
def from_tuples(cls, fieldname, value):

    if isinstance(value, tuple):
        if (len(value) == 3):
            (filename, data, content_type) = value
        else:
            (filename, data) = value
            content_type = guess_content_type(filename)
    else:
        filename = None
        content_type = None
        data = value
    request_param = cls(fieldname, data, filename=filename)
    request_param.make_multipart(content_type=content_type)
    return request_param
