# File lib/rubygems/specification.rb, line 432
    def Specification.from_yaml(input)
      input = normalize_yaml_input(input)
      spec = YAML.load(input)
      if(spec && spec.class == FalseClass) then
        raise Gem::EndOfYAMLException
      end
      unless Specification === spec
        raise Gem::Exception, "YAML data doesn't evaluate to gem specification"
      end
      unless spec.instance_variables.include? '@specification_version' and
             spec.instance_variable_get :@specification_version
        spec.instance_variable_set :@specification_version, 
          NONEXISTENT_SPECIFICATION_VERSION
      end
      spec
    end