from gekko import GEKKO
m = GEKKO()
x = m.Param(-2)
# use abs2 to define a new variable
y = m.abs2(x)
# use abs2 in an equation 
z = m.Var()
m.Equation(z==m.abs2(x)+1)
m.solve() # solve
print('x: ' + str(x.value))
print('y: ' + str(y.value))
print('z: ' + str(z.value))