Issue #2949400 by ayushmishra206, chandrashekhar_srijan, bandanasharma,...

/**

 * An interface for migrate process plugins.

 *

 * A process plugin will typically implement the transform() method to perform

 * its work. However, it is possible instead for a process plugin to use any

 * number of methods, thus offering different alternatives ways of processing.

 * In this case, the transform() method should not be implemented, and the

 * plugin configuration must provide the name of the method to be called via the

 * "method" key. Each method must have the same signature as transform().

 * The base class \Drupal\migrate\ProcessPluginBase takes care of implementing

 * transform() and calling the configured method. See

 * \Drupal\migrate\Plugin\migrate\process\SkipOnEmpty and

 * d6_field_instance_widget_settings.yml for examples.

 * Migrate process plugins transform the input value.For example, transform a

 * human provided name into a machine name, look up an identifier in a previous

 * migration and so on.

 *

 * @see \Drupal\migrate\Plugin\MigratePluginManager

 * @see \Drupal\migrate\ProcessPluginBase

 * transform a human provided name into a machine name, look up an identifier

 * in a previous migration and so on.

 *

 * Process plugins extending this class can use any number of methods, thus

 * offering different alternative ways of processing. In this case, the

 * transform() method should not be implemented, and the plugin configuration

 * must provide the name of the method to be called via the "method" key. Each

 * method must have the same signature as transform().

 *

 * @see https://www.drupal.org/node/2129651

 * @see \Drupal\migrate\Plugin\MigratePluginManager

 * @see \Drupal\migrate\Plugin\MigrateProcessInterface

 * @see \Drupal\migrate\Annotation\MigrateProcessPlugin

 * @see \Drupal\migrate\Plugin\migrate\process\SkipOnEmpty

 * @see d7_field_formatter_settings.yml

 * @see plugin_api

 *

 * @ingroup migration