add a doctest

Signed-off-by: Ziad <ziadhany2016@gmail.com>

Author: ziadhany

vulnerabilities/severity_systems.py

@@ -36,7 +36,15 @@ def as_score(self, value) -> Decimal:
         Return a normalized numeric score for this scoring system  given a raw
         value. For instance this can be used to convert a CVSS vector to a base
         score.
+
+        >>> SCORING_SYSTEMS["cvssv2_vector"].as_score("AV:L/AC:L/Au:M/C:N/I:P/A:C/E:U/RL:W/RC:ND/CDP:L/TD:H/CR:ND/IR:ND/AR:M")
+        Decimal('5.0')
+        >>> SCORING_SYSTEMS["cvssv3_vector"].as_score('CVSS:3.0/S:C/C:H/I:H/A:N/AV:P/AC:H/PR:H/UI:R/E:H/RL:O/RC:R/CR:H/IR:X/AR:X/MAC:H/MPR:X/MUI:X/MC:L/MA:X')
+        Decimal('6.5')
+        >>> SCORING_SYSTEMS["cvssv3.1_vector"].as_score("CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H")
+        Decimal('8.6')
         """
+
         if self.identifier == "cvssv2_vector":
             c = CVSS2(value)
             return c.base_score