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The plugin_type is used to register the type of the plugin. This is arbitrary, although guidelines (e.g. custom-rating) will be provided soon. The name registers the plugins name with the plugin system. 

Caveats

The database cannot be assumed to be available during plugin load time. Therefore no module-level code in the plugin file should perform any action that requires database connectivity, directly or indirectly.

Example: custom rating plugin

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