'Given a viewset, and a mapping of http methods to actions,
return a new mapping which only includes any mappings that
are actually implemented by the viewset.'

def get_method_map(self, viewset, method_map):

    bound_methods = {}
    for (method, action) in method_map.items():
        if hasattr(viewset, action):
            bound_methods[method] = action
    return bound_methods
