@fluent<EOL><INDENT>def json(self, json):<DEDENT>
self._request.json = json<EOL>self.add_matcher(matcher('<STR_LIT>', json))<EOL>
Defines the JSON body to match.

``json`` argument can be an JSON string, a JSON serializable
Python structure, such as a ``dict`` or ``list`` or it can be
a regular expression used to match the body.

Arguments:
    json (str|dict|list|regex): body JSON to match.

Returns:
    self: current Mock instance.