new_contents: from collections import OrderedDict
  
  from graphql.type.definition import GraphQLField, GraphQLNonNull
  from graphql.type.scalars import GraphQLString
  from marshmallow import fields
  
  
  class String(fields.String):
      def __init__(self, description, nullable=False, args=None,
                   deprecation_reason=None, **additional_args):
          super().__init__()
          self.description = description
          self.nullable = nullable
          self.args = args or OrderedDict()
          self.deprecation_reason = deprecation_reason
  
      def build_definition(self):
          if self.nullable:
              base_type = GraphQLString
          else:
              base_type = GraphQLNonNull(GraphQLString)
          return GraphQLField(
              type=base_type,
              args=self.args,
              deprecation_reason=self.deprecation_reason,
              description=self.description,
          )
  
subject: Implement String field