new_contents: from . import SceneObject
  
  from Cura.Math.Matrix import Matrix
  
  class Camera(SceneObject.SceneObject):
      def __init__(self, parent = None):
          super().__init__(parent)
          self._projectionMatrix = Matrix()
          self._projectionMatrix.setOrtho(-5, 5, 5, -5, -100, 100)
          #self._projectionMatrix.setPerspective(45, 1, 0, 5)
          self._locked = False
  
      def getProjectionMatrix(self):
          return self._projectionMatrix
  
      def setProjectionMatrix(self, matrix):
          self._projectionMatrix = matrix
  
      def isLocked(self):
          return self._locked
  
      def setLocked(self, lock):
          self._locked = lock
  
subject: Add a camera class