parameters: (self, eval_ctx=None)
docstring: Return the value of the expression as constant or raise
          :exc:`Impossible` if this was not possible.
  
          An :class:`EvalContext` can be provided, if none is given
          a default context is created which requires the nodes to have
          an attached environment.
  
          .. versionchanged:: 2.4
             the `eval_ctx` parameter was added.
docstring_summary: Return the value of the expression as constant or raise
          :exc:`Impossible` if this was not possible.
docstring_tokens: Return the value of the expression as constant or raise : exc : Impossible if this was not possible .
function: def as_const(self, eval_ctx=None):
          """Return the value of the expression as constant or raise
          :exc:`Impossible` if this was not possible.
  
          An :class:`EvalContext` can be provided, if none is given
          a default context is created which requires the nodes to have
          an attached environment.
  
          .. versionchanged:: 2.4
             the `eval_ctx` parameter was added.
          """
          raise Impossible()
function_tokens: def as_const ( self , eval_ctx = None ) : raise Impossible ( )