import numpy as np

def symmetric_array(arr):
    upper = np.triu(arr)
    lower = np.tril(arr.T, k=-1)
    return upper + lower
    
arr = np.array([[1, 2, 3], [2, 4, 5], [3, 5, 6]])
sym_arr = symmetric_array(arr)
print(sym_arr)