class_docstr: Base camera class.
  
  The Camera describes the perspective from which a ViewBox views its
  subscene, and the way that user interaction affects that perspective.
  
  Most functionality is implemented in subclasses. This base class has
  no user interaction and causes the subscene to use the same coordinate
  system as the ViewBox.
  
  Parameters
  ----------
  interactive : bool
      Whether the camera processes mouse and keyboard events.
  flip : tuple of bools
      For each dimension, specify whether it is flipped.
  up : {'+z', '-z', '+y', '-y', '+x', '-x'}
      The direction that is considered up. Default '+z'. Not all
      camera's may support this (yet).
  parent : Node
      The parent of the camera.
  name : str
      Name used to identify the camera in the scene.
class_docstr_tok: ["Base","camera","class",".","The","Camera","describes","the","perspective","from","which","a","ViewBox","views","its","subscene",",","and","the","way","that","user","interaction","affects","that","perspective",".","Most","functionality","is","implemented","in","subclasses",".","This","base","class","has","no","user","interaction","and","causes","the","subscene","to","use","the","same","coordinate","system","as","the","ViewBox",".","Parameters","--","--","--","--","--","interactive",":","bool","Whether","the","camera","processes","mouse","and","keyboard","events",".","flip",":","tuple","of","bools","For","each","dimension",",","specify","whether","it","is","flipped",".","up",":","{","'+z","'",",","'-z","'",",","'+y","'",",","'-y","'",",","'+x","'",",","'-x","'","}","The","direction","that","is","considered","up",".","Default","'+z","'",".","Not","all","camera","'s","may","support","this","(","yet",")",".","parent",":","Node","The","parent","of","the","camera",".","name",":","str","Name","used","to","identify","the","camera","in","the","scene","."]
code: def up(self, value):
      value = value.lower()
      value = ("+" + value) if value in "zyx" else value
      if value not in ("+z", "-z", "+y", "-y", "+x", "-x"):
          raise ValueError("Invalid value for up.")
      self._up = value
      self.view_changed()
  
imports: from __future__ import division
  from ...util import keys
  from ..node import Node
  from ...visuals.transforms import STTransform, MatrixTransform, NullTransform, TransformCache
label_desc: Use image node_id 13 for calling the BaseCamera obj's underlying member method code with example usage: obj.up(value) without return types