code: def insert(self, i, *exprs):
          
          self._assert_supports_contents()
          for j, expr in enumerate(exprs):
              self._contents.insert(i + j, expr)
docs: Insert content at specified position into expression.
  
          :param int i: Position to add content to
          :param Union[TexExpr,str] exprs: List of contents to add
  
          >>> expr = TexExpr('textbf', ('hello',))
          >>> expr
          TexExpr('textbf', ['hello'])
          >>> expr.insert(0, 'world')
          >>> expr
          TexExpr('textbf', ['world', 'hello'])