docs: def init_app(self, app):
          """Initialize the extension."""
          # Set default Flask config option.
          app.config.setdefault('STATICS_MINIFY', False)
  
          # Select resources.
          self.all_resources = ALL_RESOURCES_MINIFIED if app.config.get('STATICS_MINIFY') else ALL_RESOURCES
          self.all_variables = ALL_VARIABLES
  
          # Add this instance to app.extensions.
          if not hasattr(app, 'extensions'):
              app.extensions = dict()
          if 'statics' in app.extensions:
              raise ValueError('Already registered extension STATICS.')
          app.extensions['statics'] = _StaticsState(self, app)
  
          # Initialize blueprint.
          name = 'flask_statics_helper'
          static_url_path = '{0}/{1}'.format(app.static_url_path, name)
          self.blueprint = Blueprint(name, __name__, template_folder='templates', static_folder='static',
                                     static_url_path=static_url_path)
          self.blueprint.add_app_template_global(self.all_variables, '_flask_statics_helper_all_variables')
          self.blueprint.add_app_template_global(self.all_resources, '_flask_statics_helper_all_resources')
          app.register_blueprint(self.blueprint)