class Chef::CookbookCollection

into this.
objects for lazily-loaded remote cookbooks), it gets transformed
(e.g. CookbookLoader for solo, hash of auto-vivified Cookbook
several ways this cookbook information is collected,
This class is basically a glorified Hash, but since there are
cookbooks by name.
This class is the consistent interface for a node to obtain its
== Chef::CookbookCollection

def initialize(cookbook_versions = {})

simply extract them
The input is a mapping of cookbook name to CookbookVersion objects. We 
def initialize(cookbook_versions = {})
  super() do |hash, key|
    raise Chef::Exceptions::CookbookNotFound, "Cookbook #{key} not found. " <<
      "If you're loading #{key} from another cookbook, make sure you configure the dependency in your metadata"
  end
  cookbook_versions.each { |cookbook_name, cookbook_version| self[cookbook_name] = cookbook_version }
end

def install_gems(events) 

def install_gems(events)
  Cookbook::GemInstaller.new(self, events).install
end

def validate!

Raises:
  • (Chef::Exceptions::CookbookOhaiVersionMismatch) - if the Ohai::VERSION fails validation
  • (Chef::Exceptions::CookbookChefVersionMismatch) - if the Chef::VERSION fails validation 
def validate!
  each_value do |cookbook_version|
    cookbook_version.metadata.validate_chef_version!
    cookbook_version.metadata.validate_ohai_version!
  end
end