gym模拟的时候，
出现问题：
sim和gym的定义如下：

from isaacgym import gymapi,gymtorch
import math,random# 1. Simulation Setup
gym = gymapi.acquire_gym()# get default set of parameters
sim_params = gymapi.SimParams()
sim_params.use_gpu_pipeline=True    # load params to gpu## Simulation Parameters
# set common parameters
sim_params.dt = 1 / 60
sim_params.substeps = 2
sim_params.up_axis = gymapi.UP_AXIS_Z
sim_params.gravity = gymapi.Vec3(0.0, 0.0, -9.8)# set PhysX-specific parameters
sim_params.physx.use_gpu = True
sim_params.physx.solver_type = 1
sim_params.physx.num_position_iterations = 6
sim_params.physx.num_velocity_iterations = 1
sim_params.physx.contact_offset = 0.01
sim_params.physx.rest_offset = 0.0# set Flex-specific parameters
sim_params.flex.solver_type = 5
sim_params.flex.num_outer_iterations = 4
sim_params.flex.num_inner_iterations = 20
sim_params.flex.relaxation = 0.8
sim_params.flex.warm_start = 0.5# create sim with these parameters
sim = gym.create_sim(0, 0, gymapi.SIM_PHYSX, sim_params)