'Push values to stack at start of nesting.
When a new object scope is beginning, will push the token (type of scope)
along with the new objects value, the latter of which is provided through
the various build methods of the builder.
Args:
token: Token indicating the type of scope which is being created; must
belong to _TOKEN_VALUES.
value: Value to associate with given token.  Construction of value is
determined by the builder provided to this handler at construction.'

def _Push(self, token, value):

    self._top = (token, value)
    self._stack.append(self._top)
