code: def _check_and_expand_derivative(expr, variables, data):
      
      if re.search(r'^dd[0-9]+', expr):
          order = re.compile(r'^dd([0-9]+)').findall(expr)
          order = range(0, int(*order) + 1)
          (variables, data) = temporal_derivatives(order, variables, data)
      elif re.search(r'^d[0-9]+[\-]?[0-9]*', expr):
          order = re.compile(r'^d([0-9]+[\-]?[0-9]*)').findall(expr)
          order = _order_as_range(*order)
          (variables, data) = temporal_derivatives(order, variables, data)
      return variables, data
docs: Check if the current operation specifies a temporal derivative. dd6x
      specifies all derivatives up to the 6th, d5-6x the 5th and 6th, d6x the
      6th only.