HTTPHeaders.get_list() improve functionality

Currently if in the headers the Accept header had a value of
text/*, text/html, text/html;level=1, */*,
then
self.request.headers.get_list("Accept")
would return:
["text/*, text/html, text/html;level=1, */*"]

The documentation for get_list says:
"Returns all values for the given header as a list."

When I originally read this I thought the multiple accept types would be broken up and all added to a list such as:
["text/*", "text/html", "text/html;level=1", "*/*"]

I think that this would be much more useful and make more sense, or at least it would be in the project I'm working on.

I achieved the same effect by the following code:

response_type = self.request.headers.get_list("Accept")
response_type = [item.strip() for index in range(len(response_type)) for item in response_type[index].split(",")]

Also it would be helpful if the documentation was explicit about what's returned if the header name wasn't given.

Start at HTTPHeaders.get_list() and trace how comma-separated header values are currently returned. Check the existing documentation for get_list, then define and verify the behavior for multiple Accept values and for a missing header name, including appropriate tests if the surrounding code provides them.