code: def remove(self, expr):
          
          self._assert_supports_contents()
          index = self._contents.index(expr)
          self._contents.remove(expr)
          return index
docs: Remove a provided expression from its list of contents.
  
          :param Union[TexExpr,str] expr: Content to add
          :return: index of the expression removed
          :rtype: int
  
          >>> expr = TexExpr('textbf', ('hello',))
          >>> expr.remove('hello')
          0
          >>> expr
          TexExpr('textbf', [])