def validate_token_parameters(params):
    """Ensures token precence, token type, expiration and scope in params."""
    if 'error' in params:
        raise_from_error(params.get('error'), params)

    if not 'access_token' in params:
        raise MissingTokenError(description="Missing access token parameter.")

    if not 'token_type' in params:
        if os.environ.get('OAUTHLIB_STRICT_TOKEN_TYPE'):
            raise MissingTokenTypeError()

    # If the issued access token scope is different from the one requested by
    # the client, the authorization server MUST include the "scope" response
    # parameter to inform the client of the actual scope granted.
    # http://tools.ietf.org/html/rfc6749#section-3.3
    if params.scope_changed:
        message = 'Scope has changed from "{old}" to "{new}".'.format(
            old=params.old_scope, new=params.scope,
        )
        scope_changed.send(message=message, old=params.old_scopes, new=params.scopes)
        if not os.environ.get('OAUTHLIB_RELAX_TOKEN_SCOPE', None):
            w = Warning(message)
            w.token = params
            w.old_scope = params.old_scopes
            w.new_scope = params.scopes
            raise w
dataset/ETHPy150Open idan/oauthlib/oauthlib/oauth2/rfc6749/parameters.py/validate_token_parameters/original