code: def GetEnvironmentVariable(self, name):
      
      name = name.upper()
      return self._environment_variables.get(name, None)
docs: Retrieves an environment variable.
  
      Args:
        name (str): name of the environment variable.
  
      Returns:
        EnvironmentVariableArtifact: environment variable artifact or None
            if there was no value set for the given name.