code: def new_body(name=None, pos=None, **kwargs):
      
      if name is not None:
          kwargs["name"] = name
      if pos is not None:
          kwargs["pos"] = array_to_string(pos)
      element = ET.Element("body", attrib=kwargs)
      return element
docs: Creates a body element with attributes specified by @**kwargs.
  
      Args:
          name (str): body name.
          pos: 3d position of the body frame.