def direction_to_bounds(direction):
    """ Convert reaction direction to upper and lower bounds.

    Parameters
    ----------
    direction : {'=', '<', '>'}
        Reaction direction symbol from source file

    Returns
    -------
    tuple
        Lower bound and upper bound
    """

    if direction == '=':
        return -1000.0, 1000.0
    elif direction == '>':
        return 0.0, 1000.0
    elif direction == '<':
        return -1000.0, 0.0
    else:
        raise ValueError('Direction {0} is not valid'.format(direction))