premise: Christine Milne led the Australian Greens from 2012 until 2015. During this period, a select number of members of the parliamentary party served as official spokespersons for the party both inside and outside of Parliament on various issues, each member being assigned portfolios for their speaking duties. This allows the Greens to shadow government policies and actions from the party perspective.
hypothesis: . This allows the Greens to hide government policies and actions from the party perspective.
  
reason: I think shadow in this context means hide.