You're seeing just the function validate_schemaless_type, go back to Domo.Changeset module for more information.
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validate_schemaless_type(changeset, struct, opts \\ [])

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Validates schemaless changeset changes to conform to the schema's t() type and fulfill preconditions.

Similar to validate_type/2.

struct is a module name providing t() type and preconditions for changes validation.


{%{}, %{first_name: :string, last_name: :string, age: :integer}}
|> cast(%{last_name: "Doe", age: 21}, [:last_name, :age])
|> validate_schemaless_type(User)