class Fastlane::SupportedPlatforms

def self.all 

def self.all
  [
    :ios,
    :mac,
    :android
  ]
end

def self.verify!(platform)

this will throw an exception if the passed platform is not supported 
def self.verify!(platform)
  unless all.include? platform.to_s.to_sym
    raise "Platform '#{platform}' is not supported. Must be either #{self.all}".red
  end
end