import matplotlib.pyplot as plt

plt.figure(figsize=(3,2))
ax=plt.axes([0.1, 0.1, 0.8, 0.7])
an1 = ax.annotate("Test 1", xy=(0.5, 0.5), xycoords="data",
                  va="center", ha="center",
                  bbox=dict(boxstyle="round", fc="w"))

an2 = ax.annotate("Test 2", xy=(0.5, 1.), xycoords=an1,
                  xytext=(0.5,1.1), textcoords=(an1, "axes fraction"),
                  va="bottom", ha="center",
                  bbox=dict(boxstyle="round", fc="w"),
                  arrowprops=dict(arrowstyle="->"))
plt.show()