Create a function in Python which takes 3 arrays as input, and returns the arrays merged together into a single array.
[1, 2, 3], [4, 5, 6], [7, 8, 9]
def merge_arrays(arr1, arr2, arr3):
    combined_arr = arr1 + arr2 + arr3
    return combined_arr

result = merge_arrays([1, 2, 3], [4, 5, 6], [7, 8, 9])
print(result)