def []= (name, value)
      field = schema.fields[name.to_s] || FieldDefinition.new(name, :type => value.class)
      write_attribute(field, value, self)
    end
def []= (name, value)
      field = schema.fields[name.to_s] || FieldDefinition.new(name, :type => value.class)
      write_attribute(field, value, self)
    end
Set a field from the schema with the specified name.