ExTenant.generate_put_tenant_function

You're seeing just the macro generate_put_tenant_function, go back to ExTenant module for more information.
Link to this macro

generate_put_tenant_function(tenant_key)

View Source (macro)

generate a function signature that does this.. @tenant_key is handled through the incoming attrs

def put_tenant_id(tenant_id) do
  Process.put(@tenant_key, tenant_id)
end