Trying to fix #290. I did not know if you like exceptions or not, so, right now it will return None if the mimetype is incorrect, if you like, I can do an exception instead.
Fixed part of issue #290.
I don’t think the code needs any change. None is returned implicitly.
#290 was about documentation. json currently appears twice with different (though similar) descriptions: once through :members: in docs/api.rst and once explicitly in the same file. This is redundant.
Okay. Sorry for the trouble.