Add an input SOAP header description to the call info.

def addInHeaderInfo(self, name, type, namespace, element_type=0,
                        mustUnderstand=0):
        """Add an input SOAP header description to the call info."""
        headerinfo = HeaderInfo(name, type, namespace, element_type)
        if mustUnderstand:
            headerinfo.mustUnderstand = 1
        self.inheaders.append(headerinfo)
        return headerinfo