def _indentation(lexer, match, ctx):
    indentation = match.group(0)
    yield match.start(), Text, indentation
    ctx.last_indentation = indentation
    ctx.pos = match.end()

    if hasattr(ctx, 'block_state') and ctx.block_state and \
            indentation.startswith(ctx.block_indentation) and \
            indentation is not ctx.block_indentation:
        ctx.stack.append(ctx.block_state)
    else:
        ctx.block_state = None
        ctx.block_indentation = None
        ctx.stack.append('content')
dataset/ETHPy150Open adieu/allbuttonspressed/pygments/lexers/web.py/_indentation/operator `!=` -> `is not`