Q:

Svg Slider in console but not showing

I'm trying to build a slider svg template which I can use to switch from light theme to dark theme, The original idea is to try and replicate a design that I've seen that has a moon, then when it slides position it turns into a sun. I have build a basic template (without any graphics yet). Which I could then animate through JavaScript.
However I can't even get the basic template to show in the browser.
<?xml version="1.0" encoding="UTF-8" standalone="no"?><!--  xml:lang='en' lang='en'-->
<!DOCTYPE svg [
  <!-- entities etc. here -->
]>
<svg version="1.1"
     baseProfile="full"
     xmlns="http://www.w3.org/2000/svg"
     xmlns:xlink="http://www.w3.org/1999/xlink"
     xmlns:ev="http://www.w3.org/2001/xml-events"
     preserveAspectRatio="xMidYMid meet"
     viewBox="0 0 145 145"
     width="145" height="145" stroke="#ffffff">
        <path class="" id="a2aBdbnHKq" fill="black" stroke=""
              d="M359.91 269.76C363.84 269.76 367.03 272.95 367.03 276.88C367.03 299.29 367.03 359.4 367.03 381.81C367.03 385.75 363.84 388.93 359.91 388.93C323.48 388.93 221.3 388.93 184.87 388.93C180.94 388.93 177.75 385.75 177.75 381.81C177.75 359.4 177.75 299.29 177.75 276.88C177.75 272.95 180.94 269.76 184.87 269.76C221.3 269.76 323.48 269.76 359.91 269.76Z">
        </path>
        <path class="circ1" id="C1" fill="#c744f0" stroke=""
              d="M242.59 329.35C242.59 362.23 214.59 388.93 180.09 388.93C145.59 388.93 117.58 362.23 117.58 329.35C117.58 296.46 145.59 269.76 180.09 269.76C214.59 269.76 242.59 296.46 242.59 329.35Z">
        </path>
        <path class="rnd_rect" id="Box1" fill="#c744f0" stroke=""
              d="M418.51 329.35C418.51 362.23 390.5 388.93 356 388.93C321.5 388.93 293.49 362.23 293.49 329.35C293.49 296.46 321.5 269.76 356 269.76C390.5 269.76 418.51 296.46 418.51 329.35Z">
        </path>
        <path class="circ2" id="C2" fill="#c744f0" stroke=""
              d="M234.71 329.35C234.71 357.72 210.23 380.76 180.09 380.76C149.94 380.76 125.46 357.72 125.46 329.35C125.46 300.97 149.94 277.94 180.09 277.94C210.23 277.94 234.71 300.97 234.71 329.35Z">
        </path>
    <defs>

    </defs>

</svg>

Using W3 Document Markup Checker, the file validates and shows no errors. What have I missed?

The latest svg docs state not to use a doctype declaration, but regardless it doesn't work with or without them. It is being shown in the console, but no graphics on screen.
I know there are many questions similar to this, but every svg is different and their solutions are not working.
Also as a side question: would anyone explain what these 3 attributes are:
     xmlns:sketch="?"
     baseProfile="full"
     filterUnits="objectBoundingBox"

A:

I can't even get the basic template to show in the browser.   

I uploaded your svg file to a vector editor.  
 
The picture shows that your figure is outside the svg canvas
It is located below and to the right and its size exceeds the size of the canvas svg
Therefore, it is necessary to reduce the size of the figure and move it to the left and up 
transform="scale(0.5) translate(-120, -183)" 
Note 
The upper left corner is the origin of the SVG. The positive direction along the axis X - to the right, along the axisY - to the down

<svg version="1.1"
     baseProfile="full"
     xmlns="http://www.w3.org/2000/svg"
     xmlns:xlink="http://www.w3.org/1999/xlink"
     xmlns:ev="http://www.w3.org/2001/xml-events"
     preserveAspectRatio="xMidYMid meet"
     viewBox="0 0 145 145"
     width="50vw" height="50vh" stroke="#ffffff" style="border:1px solid red;">
       <!-- Reduce the size of the figure and move it to the left and up      -->
  <g transform="scale(0.5) translate(-120, -183)">
  <path class="" id="a2aBdbnHKq" fill="black" stroke=""
              d="M359.91 269.76C363.84 269.76 367.03 272.95 367.03 276.88C367.03 299.29 367.03 359.4 367.03 381.81C367.03 385.75 363.84 388.93 359.91 388.93C323.48 388.93 221.3 388.93 184.87 388.93C180.94 388.93 177.75 385.75 177.75 381.81C177.75 359.4 177.75 299.29 177.75 276.88C177.75 272.95 180.94 269.76 184.87 269.76C221.3 269.76 323.48 269.76 359.91 269.76Z">
        </path>
        <path class="circ1" id="C1" fill="#c744f0" stroke=""
              d="M242.59 329.35C242.59 362.23 214.59 388.93 180.09 388.93C145.59 388.93 117.58 362.23 117.58 329.35C117.58 296.46 145.59 269.76 180.09 269.76C214.59 269.76 242.59 296.46 242.59 329.35Z">
        </path>
        <path class="rnd_rect" id="Box1" fill="#c744f0" stroke=""
              d="M418.51 329.35C418.51 362.23 390.5 388.93 356 388.93C321.5 388.93 293.49 362.23 293.49 329.35C293.49 296.46 321.5 269.76 356 269.76C390.5 269.76 418.51 296.46 418.51 329.35Z">
        </path>
        <path class="circ2" id="C2" fill="#c744f0" stroke=""
              d="M234.71 329.35C234.71 357.72 210.23 380.76 180.09 380.76C149.94 380.76 125.46 357.72 125.46 329.35C125.46 300.97 149.94 277.94 180.09 277.94C210.23 277.94 234.71 300.97 234.71 329.35Z">
        </path>
 </g> 
    <defs>

    </defs>

</svg>

The red frame shows the borders of the svg canvas. Red frame can be removed after debugging the positioning.

