Our RESTful API won't be using the two modules included in the metrics/metrics/views subfolder that was generated by the app template. Thus, we must delete the metrics/metrics/views/default.py and metrics/metrics/views/notfound.py files.
Pyramid uses view callables as the main building blocks for a RESTful API. Whenever a request arrives, Pyramid finds and invokes the appropriate view callable to process the request and return an appropriate response.
View callables are callable Python objects such as functions, classes, or instances that implement a __call__ method. Any view callable receives an argument named request that will provide the pyramid.request.Request instance that represents an HTTP request.
In this case, we will work with view callable functions to process the requests related to metrics and metrics collections...
