new_contents: """Core Ros3D controller logic"""
  import logging
  from ros3ddevcontroller.param import ParametersStore
  
  
  class Controller(object):
      def __init__(self):
          self.logger = logging.getLogger(__name__)
          self.servo = None
          self.snapshots_location = None
  
      def set_servo(self, servo):
          """Servo interface"""
          self.servo = servo
  
      def set_snapshots_location(self, loc):
          """Set location of snapshots"""
          self.snapshots_location = loc
  
      def apply_param(self, param):
          """Apply parameter"""
          raise NotImplementedError('not implemented')
  
      def get_params(self):
          """Return a dict with all parameters in the system"""
          return ParametersStore.parameters_as_dict()
  
      def take_snapshot(self):
          raise NotImplementedError('not implemented')
  
      def list_snapshots(self):
          raise NotImplementedError('not implemented')
  
  
subject: add core logic class