def map_to(klass, defaults={})
      @map_to_klass = klass
    
      defaults.each do |name, value|
        self.add_attribute(name, -99).map lambda{|row, index| value}
      end
    end
def map_to(klass, defaults={})
      @map_to_klass = klass
    
      defaults.each do |name, value|
        self.add_attribute(name, -99).map lambda{|row, index| value}
      end
    end
Create a new instance with access to an evaluation context
 Each row of a CSV is parsed and mapped to a new instance of a Ruby class; Struct by default.
 Use this method to change the what class each row is mapped to.
 The given class must respond to a parameter-less #new and all attribute mappings defined.
 Providing a hash of defaults will ensure that each resulting object will have the providing name and attribute values
 unless overridden by a mapping