Finding the mean across all axes

Find the mean across all axes (that is, use the default axis = None) with this:

tf.reduce_mean(input_tensor=numbers)
#( 4. + 5. + 7. + 3.)/4 = 4.75

The output will be as follows:

<tf.Tensor: id=272, shape=(), dtype=float32, numpy=4.75>