code: def init_app(self, app):
          
          prefix_len = len(self.prefix)
          for varname, value in os.environ.items():
              if not varname.startswith(self.prefix):
                  continue
  
              # Prepare values
              varname = varname[prefix_len:]
              value = value or app.config.get(varname)
  
              # Evaluate value
              try:
                  value = ast.literal_eval(value)
              except (SyntaxError, ValueError):
                  pass
  
              # Set value
              app.config[varname] = value
docs: Initialize Flask application.