code: def tree(node, assumptions=True):
      """
      Returns a tree representation of "node" as a string.
  
      It uses print_node() together with pprint_nodes() on node.args recursively.
  
      Parameters
      ==========
  
      asssumptions : bool, optional
          The flag to decide whether to print out all the assumption data
          (such as ``is_integer`, ``is_real``) associated with the
          expression or not.
  
          Enabling the flag makes the result verbose, and the printed
          result may not be determinisitic because of the randomness used
          in backtracing the assumptions.
  
      See Also
      ========
  
      print_tree
  
      """
      subtrees = []
      for arg in node.args:
          subtrees.append(tree(arg, assumptions=assumptions))
      s = print_node(node, assumptions=assumptions) + pprint_nodes(
          subtrees
      )
      return s
  
label_desc: Use image node_id 3 for calling a global function with example usage: tree(node, assumptions) and returns: s