def from_3d_numpy_to_2d_array(X):
    """Converts 3d NumPy array (n_instances, n_columns, n_timepoints) to
    a 2d NumPy array with shape (n_instances, n_columns*n_timepoints)

    Parameters
    ----------
    X : np.ndarray
        The input 3d-NumPy array with shape
        (n_instances, n_columns, n_timepoints)

    Returns
    -------
    array_2d : np.ndarray
        A 2d-NumPy array with shape (n_instances, n_columns*n_timepoints)
    """
    array_2d = X.reshape(X.shape[0], -1)
    return array_2d