code: def evaluate_formula(formula, variables):
      
      for key, value in list(variables.items()):
          if value is None or (hasattr(value, 'isNull') and value.isNull()):
              # If one value is null, we return null.
              return value
          formula = formula.replace(key, str(value))
      result = eval(formula)
      return result
docs: Very simple formula evaluator. Beware the security.
  
      :param formula: A simple formula.
      :type formula: str
  
      :param variables: A collection of variable (key and value).
      :type variables: dict
  
      :returns: The result of the formula execution.
      :rtype: float, int