Returns the definition of a derivative plugin.
string $derivative_id: The derivative id. The id must uniquely identify the derivative within a given base plugin, but derivative ids can be reused across base plugins.
array $base_plugin_definition: The definition array of the base plugin from which the derivative plugin is derived.
array The full definition array of the derivative plugin, typically a merge of $base_plugin_definition with extra derivative-specific information. NULL if the derivative doesn't exist.
public function getDerivativeDefinition($derivative_id, array $base_plugin_definition);