human
Solve the following python programming problem given the following code:
def kf_circle() : 
    from filterpy.kalman import KalmanFilter 
    from math import radians 
    import math 
    def hx(x) : 
        radius = x [0] 
        angle = x [1] 
        x = (cos (radians (angle)) * radius) 
        y = (sin (radians (angle)) * radius) 
        return np.array ([x, y]) 
def fx(x, dt) : 
        return np.array ([x [0], (x [1] + x [2]), x [2]]) 
def hx_inv(x, y) : 
        angle = math.atan2 (y, x) 
        radius = math.sqrt (((x * x) + (y * y))) 
        return np.array ([radius, angle]) 
std_noise = 0.1 
    kf = KalmanFilter (dim_x = 3, dim_z = 2) 
    kf.x = np.array ([50.0, 0.0, 0.0]) 
    F = np.array ([[1.0, 0, 0.0], [0.0, 1.0, 1.0], [0.0, 0.0, 1.0]]) 
    kf.F = F 
    kf.P *= 100 
    kf.H = np.array ([[1, 0, 0], [0, 1, 0]]) 
    kf.R = (np.eye (2) * (std_noise ** 2)) 
    zs = [] 
    kfxs = [] 
    for t in range (0, 2000) : 
        a = ((t / 30) + 90) 
        x = ((cos (radians (a)) * 50.0) + (randn () * std_noise)) 
        y = ((sin (radians (a)) * 50.0) + (randn () * std_noise)) 
        z = hx_inv (x, y) 
        zs.append (z) 
        kf.predict () 
        kf.update (z) 
        kfxs.append (kf.x) 
zs = np.asarray (zs) 
    kfxs = np.asarray (kfxs) 
    if DO_PLOT : 
        plt.plot (zs [:, 0], zs [:, 1], c = 'r', label = 'z') 
        plt.plot (kfxs [:, 0], fx [:, 1], c = 'g', label = 'KF') 
        plt.legend (loc = 'best') 
        plt.axis ('equal') 

    
    

    Fix the buggy line: plt.plot (kfxs [:, 0], fx [:, 1], c = 'g', label = 'KF')
assistant
#Here is Python program to fix the buggy line: plt.

plt.plot (kfxs [:, 0], kfxs [:, 1], c = 'g', label = 'KF')