  where e is the error provided. e is an instance of type Error then the function will return a string in the format errorName: message where errorName and message correspond to the name and message properties of the Error object. e is not an instance of type Error then the function will return the contents of e as a string.error_to_string.test.ts located in error_to_string/src and should be run with sinon, mocha and nyc.