old_contents: from flask_sqlalchemy import SQLAlchemy
  
  db = SQLAlchemy()
  
  class Unit(db.Model):
      table = db.Column(db.String(), primary_key=True)
      field = db.Column(db.String(), primary_key=True)
      unit = db.Column(db.String(), primary_key=True)
  
  class Simulation(db.Model):
      date = db.Column(db.DateTime(), primary_key=True) # datetime object
      globalSolar = db.Column(db.String())
      PVPowerOutput = db.Column(db.Float())
      ACPrimaryLoad = db.Column(db.Float())
      ACPrimaryLoadServed = db.Column(db.Float())
      gridPowerPrice = db.Column(db.Float())
      gridSellbackRate = db.Column(db.Float())
      gridPurchases = db.Column(db.Float())
      gridSales = db.Column(db.Float())
      totalElectricalLoadServed = db.Column(db.Float())
      renewablePresentation = db.Column(db.Float())
      excessElectricalProduction = db.Column(db.Float())
      unmetElectricalLoad = db.Column(db.Float())
      totalRenewablePowerOutput = db.Column(db.Float())
      inverterPowerInput = db.Column(db.Float())
      inverterPowerOutput = db.Column(db.Float())
      ACRequiredOperatingCapacity = db.Column(db.Float())
      DCRequiredOperatingCapacity = db.Column(db.Float())
      ACOperatingCapacity = db.Column(db.Float())
      DCOperatingCapacity = db.Column(db.Float())
  
      def __init__(self, **kwargs):
          for key, value in kwargs.items():
              setattr(self, key, value)
  
      def getRange(start, end):
          return Simulation.query.filter(Simulation.date >= start).\
              filter(Simulation.date <= end)
  
new_contents: from flask_sqlalchemy import SQLAlchemy
  
  db = SQLAlchemy()
  
  class Unit(db.Model):
      table = db.Column(db. String(), primary_key=True)
      field = db.Column(db.String(), primary_key=True)
      unit = db.Column(db.String())
  
  class Simulation(db.Model):
      timestamp = db.Column(db.DateTime(), primary_key=True) # datetime object
      globalSolar = db.Column(db.String())
      PVPowerOutput = db.Column(db.Float())
      ACPrimaryLoad = db.Column(db.Float())
      ACPrimaryLoadServed = db.Column(db.Float())
      gridPowerPrice = db.Column(db.Float())
      gridSellbackRate = db.Column(db.Float())
      gridPurchases = db.Column(db.Float())
      gridSales = db.Column(db.Float())
      totalElectricalLoadServed = db.Column(db.Float())
      renewablePresentation = db.Column(db.Float())
      excessElectricalProduction = db.Column(db.Float())
      unmetElectricalLoad = db.Column(db.Float())
      totalRenewablePowerOutput = db.Column(db.Float())
      inverterPowerInput = db.Column(db.Float())
      inverterPowerOutput = db.Column(db.Float())
      ACRequiredOperatingCapacity = db.Column(db.Float())
      DCRequiredOperatingCapacity = db.Column(db.Float())
      ACOperatingCapacity = db.Column(db.Float())
      DCOperatingCapacity = db.Column(db.Float())
  
      def __init__(self, **kwargs):
          for key, value in kwargs.items():
              setattr(self, key, value)
  
      def getRange(start, end):
          return Simulation.query.filter(Simulation.date >= start).\
              filter(Simulation.date <= end)
  
subject: Update Simulation model to have timestamp attribute