title: bitbake: d.getVar("X", True) what does True mean?
body: <p>I find the following:</p>
  
  <p><a href="http://www.yoctoproject.org/docs/2.1/bitbake-user-manual/bitbake-user-manual.html#accessing-datastore-variables-using-python" rel="noreferrer">http://www.yoctoproject.org/docs/2.1/bitbake-user-manual/bitbake-user-manual.html#accessing-datastore-variables-using-python</a></p>
  
  <p>It said that: Using "expand=True" expands the value. What does the "expand" means? </p>