Find the predefined readlength closest to the estimated readlength.

    In the case of a tie, choose the shortest readlength.

def get_closest_readlength(estimated_readlength):
    # type: (int) -> int
    """Find the predefined readlength closest to the estimated readlength.

    In the case of a tie, choose the shortest readlength."""

    readlengths = [36, 50, 75, 100]
    differences = [abs(r - estimated_readlength) for r in readlengths]
    min_difference = min(differences)
    index_of_min_difference = [i
                               for i, d in enumerate(differences)
                               if d == min_difference][0]

    return readlengths[index_of_min_difference]