Add some documentation to do the top of lassen.py

"""

Reference:

    Patki, Tapasya, et al. "Monitoring large scale supercomputers: A case study with the Lassen supercomputer." 

    2021 IEEE International Conference on Cluster Computing (CLUSTER). IEEE, 2021.

Instructions:

    git clone https://github.com/LLNL/LAST/ && cd LAST

    git lfs pull

    # to analyze dataset

    python -m raps.telemetry -f /path/to/LAST/Lassen-Supercomputer-Job-Dataset --system lassen -v

    # to simulate the dataset    

    python main.py -f /path/to/LAST/Lassen-Supercomputer-Job-Dataset --system lassen

    # to reschedule

    python main.py -f /path/to/LAST/Lassen-Supercomputer-Job-Dataset --system lassen --reschedule

    # to fast-forward 37 days and replay for 1 day

    python main.py -f /path/to/LAST/Lassen-Supercomputer-Job-Dataset --system lassen -ff 37d -t 1d

"""

import math

import numpy as np

import os