docstr: Add an item to the canvas. 
docstr_tok: ["Add","an","item","to","the","canvas","."]
code: def addItem(self, citem):
      """
      Add an item to the canvas.
      """
  
      ## Check for redirections
      if self.redirect is not None:
          name = self.redirect.addItem(citem)
          self.items.append(citem)
          return name
  
      if not self.allowTransforms:
          citem.setMovable(False)
  
      citem.sigTransformChanged.connect(self.itemTransformChanged)
      citem.sigTransformChangeFinished.connect(
          self.itemTransformChangeFinished
      )
      citem.sigVisibilityChanged.connect(self.itemVisibilityChanged)
  
      ## Determine name to use in the item list
      name = citem.opts["name"]
      if name is None:
          name = "item"
  
      ## find parent and add item to tree
      insertLocation = 0
  
      ## determine parent list item where this item should be inserted
      parent = citem.parentItem()
      if parent in (None, self.view.childGroup):
          parent = self.itemList.invisibleRootItem()
      else:
          parent = parent.listItem
  
      ## set Z value above all other siblings if none was specified
      siblings = [
          parent.child(i).canvasItem()
          for i in range(parent.childCount())
      ]
      z = citem.zValue()
      if z is None:
          zvals = [i.zValue() for i in siblings]
          if parent is self.itemList.invisibleRootItem():
              if len(zvals) == 0:
                  z = 0
              else:
                  z = max(zvals) + 10
          else:
              if len(zvals) == 0:
                  z = parent.canvasItem().zValue()
              else:
                  z = max(zvals) + 1
          citem.setZValue(z)
  
      ## determine location to insert item relative to its siblings
      for i in range(parent.childCount()):
          ch = parent.child(i)
          zval = (
              ch.canvasItem().graphicsItem().zValue()
          )  ## should we use CanvasItem.zValue here?
          if zval < z:
              insertLocation = i
              break
          else:
              insertLocation = i + 1
  
      node = QtWidgets.QTreeWidgetItem([name])
      flags = (
          node.flags()
          | QtCore.Qt.ItemFlag.ItemIsUserCheckable
          | QtCore.Qt.ItemFlag.ItemIsDragEnabled
      )
      if not isinstance(citem, GroupCanvasItem):
          flags = flags & ~QtCore.Qt.ItemFlag.ItemIsDropEnabled
      node.setFlags(flags)
      if citem.opts["visible"]:
          node.setCheckState(0, QtCore.Qt.CheckState.Checked)
      else:
          node.setCheckState(0, QtCore.Qt.CheckState.Unchecked)
  
      node.name = name
      parent.insertChild(insertLocation, node)
  
      citem.name = name
      citem.listItem = node
      node.canvasItem = weakref.ref(citem)
      self.items.append(citem)
  
      ctrl = citem.ctrlWidget()
      ctrl.hide()
      self.ui.ctrlLayout.addWidget(ctrl)
  
      ## inform the canvasItem that its parent canvas has changed
      citem.setCanvas(self)
  
      ## Autoscale to fit the first item added (not including the grid).
      if len(self.items) == 2:
          self.autoRange()
  
      return citem
  
imports: import gc
  import importlib
  import weakref
  import warnings
  from ..graphicsItems.GridItem import GridItem
  from ..graphicsItems.ROI import ROI
  from ..graphicsItems.ViewBox import ViewBox
  from ..Qt import QT_LIB, QtCore, QtGui, QtWidgets
  from .None import CanvasTemplate_generic
  from .CanvasItem import CanvasItem, GroupCanvasItem
  from .CanvasManager import CanvasManager
label_desc: Use image node_id 22 for calling the Canvas obj's underlying member method code with example usage: obj.addItem(citem) and returns: citem, name