Problem in understanding the function signature

Moralis General
#1

Hi,
I have got the following code:

function GasCost(string memory name, 
    function () internal returns (string memory) fun) 
    internal returns (string memory) 
{
    uint u0 = gasleft();
    string memory sm = fun();
    uint u1 = gasleft();
    uint diff = u0 - u1;
    return concat(name, " GasCost: ", stringOfUint(diff), 
                " returns(", sm, ")");
}

Somebody please explain me what is the name of the above function defining technique? and how to invoke such functions? Provide me the link for the tutorial also.
Zulfi.

#2

what do you see in the abi for that function?

#3

Hi,
Sorry it is not a complete program.

Zulfi.