def param_defs(self, method):
raise Exception('<STR_LIT>')<EOL>
Get parameter definitions.  
Each I{pdef} is a tuple (I{name}, L{xsd.sxbase.SchemaObject})
@param method: A servic emethod.
@type method: I{service.Method}
@return: A collection of parameter definitions
@rtype: [I{pdef},..]