def crop_beginning(data):
    """Crop constant padding at the begin of the data column"""
    assert data.shape[1] == 2
    start = data[0, 1]
    for ii in range(1, data.shape[0]):
        if data[ii, 1] != start:
            break
    else:
        raise ValueError('Encountered all-constant data!')
    return data[ii - 1:, :]
