from typing import Optional


def line_intersection(
    m_1: float, b_1: float, m_2: float, b_2: float,
) -> Optional[float]:
    """
    Returns a float representing the x-ordinate of the intersection
    point of the lines defined by y = m_1*x + b_1 and y = m_2*x + b_2.

    Returns None if the lines are parallel.
    """
    try:
        x = (b_2 - b_1) / (m_1 - m_2)
    except ZeroDivisionError:
        x = None
    return x