code: def _get_version(self):
          
          if "version" in self.document.attrib:
              value = self.document.attrib["version"].lower()
              if value in allowed_versions[self.params['service']]:
                  self.params["version"] = value
              else:
                  raise OWSInvalidParameterValue("Version %s is not supported" % value, value="version")
          elif self._get_request_type() == "getcapabilities":
              self.params["version"] = None
          else:
              raise OWSMissingParameterValue('Parameter "version" is missing', value="version")
          return self.params["version"]
docs: Find requested version in POST request.