[Lua] Getting the table a function is called from

So, I am practicing creating an API and I was wondering how you get the name of the table that a function is called from.
The way it works is supposed to be similar to the fs API so you can do:

ThingA = newMatrix()

where new matrix returns a table containing a bunch of functions

the you could do

ThingA:newRow()

where newRow is a function in the table "ThingA"

But, newRow requires the name of "ThingA" to be able to insert a new row into it.

How do get the name of the table "ThingA" without having to type

ThingA:newRow(ThingA)

?

The colon notation like you have there passes the table immediately before the colon (in your example, ThingA) as the first parameter to the function. This is usually caught in a variable named self. So:

function doStuff(self, entry)
  if not self.values then self.values = {}
  table.insert(self.values, entry)
end

Awesome thanks