how can I access @asset s metadata in an IOManager?

You should be able to access it by passing in the context. I'm semi working on a POC with dagster for our new ETL pipelines but have switched another project so I haven't had to much time to look at it so this code may be out of date.

class SomeIOManager(ConfigurableIOManager):
    def handle_output(self, context, df: DataFrame):
        context.metadata['some_key']