code: def get_schema_field(schema, field):
      
      schema_fields_to_model = {key: get_model_field(schema, key) for (key, value) in schema._declared_fields.items()}
      for key, value in schema_fields_to_model.items():
          if value == field:
              return key
  
      raise Exception("Couldn't find schema field from {}".format(field))
docs: Get the schema field of a model field
  
      :param Schema schema: a marshmallow schema
      :param str field: the name of the model field
      :return str: the name of the field in the schema