docs: def isin(self, values):
          """ Selects the samples having the metadata attribute between the values provided
          as input
  
          :param values: a list of elements
          :return a new complex condition
          """
          if not isinstance(values, list):
              raise TypeError("Input should be a string. {} was provided".format(type(values)))
          if not (self.name.startswith("(") and self.name.endswith(")")):
              first = True
              new_condition = None
              for v in values:
                  if first:
                      first = False
                      new_condition = self.__eq__(v)
                  else:
                      new_condition = new_condition.__or__(self.__eq__(v))
              return new_condition
          else:
              raise SyntaxError("You cannot use 'isin' with a complex condition")