parameters: (self, nstep)
docstring: Initialize the tree structure for hack force calculation.
          @param nsteps the current time step
docstring_summary: Initialize the tree structure for hack force calculation.
docstring_tokens: Initialize the tree structure for hack force calculation .
function: def make_tree(self, nstep):
          """
          Initialize the tree structure for hack force calculation.
          @param nsteps the current time step
          """
          for q in reversed(self.bodies):
              if q.mass != 0.0:
                  q.expand_box(self, nstep)
                  xqic = self.int_coord(q.pos)
                  if self.root is None:
                      self.root = q
                  else:
                      self.root = self.root.load_tree(q, xqic, Node.IMAX >> 1, self)
          self.root.hack_cofm()
function_tokens: def make_tree ( self , nstep ) : for q in reversed ( self . bodies ) : if q . mass != 0.0 : q . expand_box ( self , nstep ) xqic = self . int_coord ( q . pos ) if self . root is None : self . root = q else : self . root = self . root . load_tree ( q , xqic , Node . IMAX >> 1 , self ) self . root . hack_cofm ( )