Implement Tangent Stiffness Matrix as function of elemental cross-section areas about trusspy HOT 2 CLOSED

import trusspy as tp

def create_model():
    '''Create a TrussPy-Model and return the Model instance.'''
    M = tp.Model(log=0)
    
    with M.Nodes as MN:
        MN.add_node( 1, coord=( 0, 0, 0))
        MN.add_node( 2, coord=( 1, 0, 1))
        MN.add_node( 3, coord=( 2, 0, 0))
    
    with M.Elements as ME:
        ME.add_element( 1, conn=(1,2), gprop=[1] )
        ME.add_element( 2 ,conn=(2,3), gprop=[1] )
        ME.assign_material( 'all', [1])
    
    with M.Boundaries as MB:
        MB.add_bound_U( 1, (0,0,0) )
        MB.add_bound_U( 2, (0,0,1) )
        MB.add_bound_U( 3, (0,0,0) )
    
    with M.ExtForces as MF:
        MF.add_force( 2, ( 0, 0,-1) )
        
    M.Settings.incs = 1
    return M

def stiffness(list_of_areas):
    '''Calculate the stiffness matrix as a function of elemental
    cross-section areas (passed as list).'''
    
    M = create_model()
    M.Elements.assign_geometries('all', list_of_areas)
    
    M.build()
    M.run()
    
    R0 = M.Results.R[0]
    # return K (full system), Kred (only active DOF) 
    # or Kmod (see Documentation)
    return R0.Kred

list_of_areas = [2,3]
K = stiffness(list_of_areas)