class_docstr: Abstract base class for all actuator classes to inherit from.
  
  Notes
  =====
  
  Instances of this class cannot be directly instantiated by users. However,
  it can be used to created custom actuator types through subclassing.
docstr: Default representation of an actuator.
docstr_tok: ["Default","representation","of","an","actuator","."]
code: def __repr__(self):
      """Default representation of an actuator."""
      return f"{self.__class__.__name__}()"
  
imports: from abc import ABC, abstractmethod
  from sympy import S, sympify
  from sympy.physics.mechanics.joint import PinJoint
  from sympy.physics.mechanics.loads import Torque
  from sympy.physics.mechanics.pathway import PathwayBase
  from sympy.physics.mechanics.rigidbody import RigidBody
  from sympy.physics.vector import ReferenceFrame, Vector
label_desc: Use image node_id 3 for calling the ActuatorBase obj's underlying member method code with example usage: obj.__repr__() and returns: self, str