How to reference TMPRO button

Well this isn't clear to me
Looked high & Low

How does one reference a "Button - TextMeshPro"

I know

"Text - TextMeshPro" is:
.GetComponent<TMPro.TextMeshProUGUI>()

and even
a "dropdown - TextMeshPro" is
.GetComponent<TMPro.TMP_Dropdown>()

but what is the equivalent for the button please. Documentation on this i cannot find!