function freeBuffers(defs) {
              var _iteratorNormalCompletion = true;
              var _didIteratorError = false;
              var _iteratorError = undefined;
              try {
                for (
                  var _iterator = defs[Symbol.iterator](), _step;
                  !(_iteratorNormalCompletion = (_step = _iterator.next()).done);
                  _iteratorNormalCompletion = true
                ) {
                  var def = _step.value;
                  if (buffers[def.dst]) {
                    gl.deleteBuffer(buffers[def.dst]);
                    buffers[def.dst] = null;
                  }
                }
              } catch (err) {
                _didIteratorError = true;
                _iteratorError = err;
              } finally {
                try {
                  if (!_iteratorNormalCompletion && _iterator.return != null) {
                    _iterator.return();
                  }
                } finally {
                  if (_didIteratorError) {
                    throw _iteratorError;
                  }
                }
              }
            }
creates a buffers object that holds the WebGL render buffers
for a geometry.
@private
@param  {String} gId    key of the geometry object
@param  {p5.Geometry}  model contains geometry data