code: func (a *Assertions) Contains(s interface{}, contains interface{}, msgAndArgs ...interface{}) {
  	if h, ok := a.t.(tHelper); ok {
  		h.Helper()
  	}
  	Contains(a.t, s, contains, msgAndArgs...)
  }
docs: // Contains asserts that the specified string, list(array, slice...) or map contains the
  // specified substring or element.
  //
  //    a.Contains("Hello World", "World")
  //    a.Contains(["Hello", "World"], "World")
  //    a.Contains({"Hello": "World"}, "Hello")