code: def _is_autonomous(indep, exprs):
      
      if indep is None:
          return True
      for expr in exprs:
          try:
              in_there = indep in expr.free_symbols
          except:
              in_there = expr.has(indep)
          if in_there:
              return False
      return True
docs: Whether the expressions for the dependent variables are autonomous.
  
      Note that the system may still behave as an autonomous system on the interface
      of :meth:`integrate` due to use of pre-/post-processors.