code: def get_model_field(schema, field):
      
      if schema._declared_fields.get(field) is None:
          raise Exception("{} has no attribute {}".format(schema.__name__, field))
  
      if schema._declared_fields[field].attribute is not None:
          return schema._declared_fields[field].attribute
      return field
docs: Get the model field of a schema field
  
      :param Schema schema: a marshmallow schema
      :param str field: the name of the schema field
      :return str: the name of the field in the model