code: def _slice_value(index, context=None):
      
  
      if isinstance(index, Const):
          if isinstance(index.value, (int, type(None))):
              return index.value
      elif index is None:
          return None
      else:
          # Try to infer what the index actually is.
          # Since we can't return all the possible values,
          # we'll stop at the first possible value.
          try:
              inferred = next(index.infer(context=context))
          except exceptions.InferenceError:
              pass
          else:
              if isinstance(inferred, Const):
                  if isinstance(inferred.value, (int, type(None))):
                      return inferred.value
  
      # Use a sentinel, because None can be a valid
      # value that this function can return,
      # as it is the case for unspecified bounds.
      return _SLICE_SENTINEL
docs: Get the value of the given slice index.