Inconsistent documentation about HTTPPropagator usage

[yatishb]

The docs on injecting the context attributes for propagation of HTTP requests states that the inject() can be called on the HTTPPropagator class as follows:

def parent_call():
  with tracer.trace("parent_span") as span:
    headers = {}
    HTTPPropagator.inject(span.context, headers)
    url = "<some RPC endpoint>"
    r = requests.get(url, headers=headers)

When doing this, I get an error that the method HTTPPropagator.inject() requires an instance to be passed. Looking at the code, inject() is not a classmethod or a staticmethod, and the example should be updated to:

def parent_call():
  with tracer.trace("parent_span") as span:
    headers = {}
    propagator = HTTPPropagator()
    propagator.inject(span.context, headers)
    url = "<some RPC endpoint>"
    r = requests.get(url, headers=headers)

The same follows for the extract() method as well.

[Kyle-Verhoog]

@yatishb good catch. We'll add this to our documentation fixes we're working on, thanks!

[palazzem]

Fixed with #539 . The new document will be shipped today! Thank you very much for pointing out the problem.