Private method to calculate NMMDS embedding
    :param dimensions: (int)
    :return: coordinate matrix (np.array)

def _embedding_nonmetric_mds(matrix, dimensions=3, initial_coords=None):
    """
    Private method to calculate NMMDS embedding
    :param dimensions: (int)
    :return: coordinate matrix (np.array)
    """
    mds = sklearn.manifold.MDS(n_components=dimensions,
                               dissimilarity='precomputed',
                               metric=False)
    if initial_coords is not None:
        mds.fit(matrix, init=initial_coords)
    else:
        mds.fit(matrix)
    return mds.embedding_