environment varialbels not working in postman code example

Example 1: accesing variables in api

You can use double curly braces to reference variables 
throughout the Postman user interface. For example, 
to reference a variable named "username" in your request
 settings, you could use the following syntax with
double curly braces around the name:

{{username}}

Example 2: defining collection variables

Use pm.collectionVariables to define a collection variable:

pm.collectionVariables.set("variable_key", "variable_value");