code: def find_secondary_sources(
      assignment_nodes,
      sources,
      lattice
  ):
      
      for source in sources:
          source.secondary_nodes = find_assignments(assignment_nodes, source, lattice)
docs: Sets the secondary_nodes attribute of each source in the sources list.
  
          Args:
              assignment_nodes([AssignmentNode])
              sources([tuple])
              lattice(Lattice): the lattice we're analysing.