code: def insert(self, i, *nodes):
          r
          assert isinstance(i, int), (
                  'Provided index "{}" is not an integer! Did you switch your '
                  'arguments? The first argument to `insert` is the '
                  'index.'.format(i))
          self.expr.insert(i, *nodes)
docs: r"""Add node(s) to this node's list of children, inserted at position i.
  
          :param int i: Position to add nodes to
          :param TexNode nodes: List of nodes to add
  
          >>> from TexSoup import TexSoup
          >>> soup = TexSoup(r'''
          ... \begin{itemize}
          ...     \item Hello
          ...     \item Bye
          ... \end{itemize}''')
          >>> item = soup.item
          >>> soup.item.delete()
          >>> soup.itemize.insert(1, item)
          >>> soup.itemize
          \begin{itemize}
              \item Hello
              \item Bye
          \end{itemize}