def concatenate(tensors, axis=-1):
    if axis < 0:
        if len(tensors[0].get_shape()):
            axis = axis % len(tensors[0].get_shape())
        else:
            axis = 0
    return tf.concat(axis, tensors)
Concantes a list of tensors alongside the specified axis.
dataset/ETHPy150Open fchollet/keras/keras/backend/tensorflow_backend.py/concatenate