class: PackageDeliveriesTracker
responsability: starting point of the program. Handles the displaying and modifying opperations of different kinds of packages. Load and store packages to json.
collaborators: textMenu, PackageFactory

class: textMenu
responsability: Displays operations to be performed for packages. Take user input for the operations and returns the status.
collaborators: PackageDeliveriesTracker, PackageInfo,

class: PackageInfo
responsability: define the attributes of packages. Allow for accessing and motifying fields of package info.
collaborators: BookPackage, PerishablePackage, ElectronicPackage, PackageFactory

class: PackageFactory
responsability: initialize and return an instance of one of the package types.
collaborators: BookPackage, PerishablePackage, ElectronicPackage

class: BookPackage
responsability: Sub class of PackageInfo. Defines the field author name and allows modification.
collaborators: PackageFactory, PackageDeliveriesTracker

class: PerishablePackage
responsability: Sub class of PackageInfo. Defines the field expiry date and allows modification.
collaborators: PackageFactory, PackageDeliveriesTracker

class: ElectronicPackage
responsability: Sub class of PackageInfo. Defines the field enviremental handling fee and allows modification.
collaborators: PackageFactory, PackageDeliveriesTracker