error when input function called with shape (2,2)
x, y that goes in tf.estimator.inputs.numpy_input_fn() must be either an array or a dictionary of arrays. Quoting from the link (https://www.tensorflow.org/api_docs/python/tf/estimator/inputs/numpy_input_fn) - x: numpy array object or dict of numpy array objects. If an array, the array will be treated as a single feature. 

So in your case it is treating 'feature' as a single feature. You can try this:

x1 = np.array([-1,-2])

x2 = np.array([1,2])

features = {'x1': x1, 'x2': x2}