Give me an example of an op that uses the output of an upstream op as its input

In Dagster, we prefer to use the term "asset" over "op" when discussing dependencies and data flow. Assets in Dagster represent a piece of data and its computation, and they can depend on other assets. When one asset depends on another, the output of the upstream asset is used as the input for the downstream asset. Here's an example from the documentation that illustrates how you can define assets that depend on each other:

python from dagster import asset  @asset def upstream_asset():     # Perform some computation     return "upstream_data"  @asset def downstream_asset(upstream_asset):     # Use the output of upstream_asset as input     return f"downstream_data based on {upstream_asset}"

In this example,

downstream_asset

uses the output of

upstream_asset

as its input. When

downstream_asset

is computed, Dagster ensures that

upstream_asset

has already been computed and uses its output as the input for

downstream_asset

. This is how dependencies between assets are managed in Dagster, allowing for clear data lineage and dependency tracking.