def extract_templates(config)
      templates_hosts = config['HOSTS'].values.group_by { |h| h['template'] }
      templates_hosts.each do |template, hosts|
        templates_hosts[template] = hosts.count
      end
    end
def extract_templates(config)
      templates_hosts = config['HOSTS'].values.group_by { |h| h['template'] }
      templates_hosts.each do |template, hosts|
        templates_hosts[template] = hosts.count
      end
    end
Given an existing, fully-specified host configuration, count the number of
 hosts using each template, and return a map of template name to host count.

 For example, given the following config (parts omitted for brevity):
    {"HOSTS"=>
     {"centos6-64-1"=>
        {"template"=>"centos-6-x86_64", ...},
      "redhat7-64-1"=>
        {"template"=>"redhat-7-x86_64", ...},
      "centos6-64-2"=>
        {"template"=>"centos-6-x86_64", ...}},
     ...
    }}

 Returns the following map:
     {"centos-6-x86_64"=>2, "redhat-7-x86_64"=>1}