dependencies:
    enforced:
      module:
        - yourmodule

langcode: en
status: true
dependencies:
  module:
    - node
    - my_module
id: node.my_module
label: 'My Module'
targetEntityType: node
cache: true

$entity_type="node"; //The entity for which you want to create the view mode
$view_mode="example"; //The name of the new view mode
$settings=Array();
$settings["id"]=$entity_type.".".$view_mode;
$settings["targetEntityType"]=$entity_type;
$evm=DrupalCoreEntityEntityEntityViewMode::create($settings);
$evm->save();