MoveIt create PlanningSceneInterface

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I am trying to retrieve a collision object that is present in the moveit planning scene to then attach it to a robot link. To do this, I thought of getting the object by its ID using the getObjects method of the PlanningSceneInterface class. However, when I try to create an object of the PlanningSceneInterface class I get the following error:

error: ‘moveit::planning_interface’ has not been declared
 moveit::planning_interface::PlanningSceneInterface scene_interface;

I am including the class with the following line:

#include <moveit/planning_interface/planning_interface.h>

I am running ROS Melodic on Ubuntu 18.04, with gcc 7.5.0.

Thanks in advance!