code: def set_guest_property_value(self, property_p, value):
          
          if not isinstance(property_p, basestring):
              raise TypeError("property_p can only be an instance of type basestring")
          if not isinstance(value, basestring):
              raise TypeError("value can only be an instance of type basestring")
          self._call("setGuestPropertyValue",
                       in_p=[property_p, value])
docs: Sets or changes a value in the machine's guest property
          store. The flags field will be left unchanged or created empty for a
          new property.
  
          in property_p of type str
              The name of the property to set or change.
  
          in value of type str
              The new value of the property to set or change. If the
              property does not yet exist and value is non-empty, it will be
              created.
  
          raises :class:`OleErrorAccessdenied`
              Property cannot be changed.
          
          raises :class:`VBoxErrorInvalidVmState`
              Virtual machine is not mutable or session not open.
          
          raises :class:`VBoxErrorInvalidObjectState`
              Cannot set transient property when machine not running.