You're seeing just the function discriminator, go back to PhoenixSwagger.Schema module for more information.
Link to this function

discriminator(model, property_name)

View Source

Specifies the name of a property that identifies the polymorphic schema for a JSON object.

The value of this property should be the name of this schema, or another schema that inherits from this schema using all_of.



iex> alias PhoenixSwagger.Schema
...> %Schema{}
...> |> Schema.type(:object)
...> |> Schema.title("Pet")
...> |>, :string, "polymorphic pet schema type", example: "Dog")
...> |> Schema.discriminator(:pet_type)
  type: :object,
  title: "Pet",
  properties: %{
    pet_type: %Schema{
      type: :string,
      description: "polymorphic pet schema type",
      example: "Dog"
  discriminator: :pet_type,
  required: [:pet_type]