Parse a YAML specification of a condition into this object.

def parse_yaml(self, y):
        '''Parse a YAML specification of a condition into this object.'''
        self.sequence = int(y['sequence'])
        self.target_component = \
                TargetExecutionContext().parse_yaml(y['targetComponent'])
        if RTS_EXT_NS_YAML + 'properties' in y:
            for p in y.get(RTS_EXT_NS_YAML + 'properties'):
                if 'value' in p:
                    value = p['value']
                else:
                    value = None
                self._properties[p['name']] = value
        return self