'Parse `args.items` into `args.headers`, `args.data`, `args.params`,
and `args.files`.'

def _parse_items(self):

    try:
        items = parse_items(items=self.args.items, data_class=(ParamsDict if self.args.form else OrderedDict))
    except ParseError as e:
        if self.args.traceback:
            raise
        self.error(e.args[0])
    else:
        self.args.headers = items.headers
        self.args.data = items.data
        self.args.files = items.files
        self.args.params = items.params
    if (self.args.files and (not self.args.form)):
        file_fields = list(self.args.files.keys())
        if (file_fields != ['']):
            self.error(('Invalid    file    fields    (perhaps    you    meant    --form?):    %s' % ','.join(file_fields)))
        (fn, fd, ct) = self.args.files['']
        self.args.files = {}
        self._body_from_file(fd)
        if ('Content-Type' not in self.args.headers):
            content_type = get_content_type(fn)
            if content_type:
                self.args.headers['Content-Type'] = content_type
