code: def guess_fill_char( left_comp, right_comp ):
      
      # No left component, obiously new
      return "*"
      # First check that the blocks have the same src (not just species) and 
      # orientation
      if ( left_comp.src == right_comp.src and left_comp.strand != right_comp.strand ): 
          # Are they completely contiguous? Easy to call that a gap
          if left_comp.end == right_comp.start: 
              return "-"
          # TODO: should be able to make some guesses about short insertions
          # here
      # All other cases we have no clue about
      return "*"
docs: For the case where there is no annotated synteny we will try to guess it