<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_data_len(self):
 # type: () -> int """ get_data_len computes the length of the data field To do this computation, the length of the padlen field and the actual padding is subtracted to the string that was provided to the pre_dissect # noqa: E501 fun of the pkt parameter @return int; length of the data part of the HTTP/2 frame packet provided as parameter # noqa: E501 @raise AssertionError """

        padding_len = self.getfieldval('padlen')
        fld, fval = self.getfield_and_val('padlen')
        padding_len_len = fld.i2len(self, fval)

        ret = self.s_len - padding_len_len - padding_len
        assert(ret >= 0)
        return ret