def _CombineContext(self):
    # Context can merge from item 0
    for i in range(1 - len(self.stack), 0, -1):
      item = self.stack[i - 1]
      if (isinstance(item, ContextExpression) and
          isinstance(self.stack[i], lexer.Expression)):
        expression = self.stack[i]
        self.stack[i - 1].SetExpression(expression)
        self.stack[i] = None

    self.stack = filter(None, self.stack)


# FILTER IMPLEMENTATIONS
dataset/ETHPy150Open google/grr/grr/lib/objectfilter.py/Parser._CombineContext/swapped operands of `-`