PYTHON HELP PLEASE!!!

(Please fix code below, I am coming up with error code: expected an indented block after line marked in bold. see pic....)

import numpy as np

import matplotlib.pyplot as plt

def time_to_hit_ground(y0, v0, a):

discriminant = np.sqrt(v0**2 - 2*a*y0)

t1 = (-v0 - discriminant) / a

t2 = (-v0 + discriminant) / a

if t1 >=0:

return t1

return t2

def drop(y0, v0=0.0, dt=0.1, g=-9.8):

if y0

print('Object is underground.')

return

# if you also allow the user to change `dt` and `g` from the arguments,

t_ground = time_to_hit_ground(y0, v0, g)

t = np.arange(0, t_ground+dt, dt)

v = v0 + g * t

y = y0 + v0 * t + g * t**2 / 2.

plt.plot(t, y, '.')

plt.axvline(t_ground, color='g')

plt.axhline(0, color='g')

plt.xlabel('Time (s)')

plt.ylabel('Height (m)')

plt.title('ANVIL')

plt.show()

if t1 >=0: SyntaxError return tl return t2 expected an indented block def drop ( yo, vo-o.o, dt=0.1, g=-9.8): if yo