GenServer.abcast

You're seeing just the function abcast, go back to GenServer module for more information.
Link to this function

abcast(nodes \\ [node() | Node.list()], name, request)

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Specs

abcast([node()], name :: atom(), term()) :: :abcast

Casts all servers locally registered as name at the specified nodes.

This function returns immediately and ignores nodes that do not exist, or where the server name does not exist.

See multi_call/4 for more information.