[graph-tool] get_out_degrees function issue

Hi, I'm trying to use the function "get_out_degrees", but I get following error: AttributeError: 'Graph' object has no attribute 'get_out_degrees' The graph I generated is a directed graph: <Graph object, directed, with 396 vertices and 10042 edges at 0x7fb5c15c5690> The gt version is the 2.18 (Ubuntu Trusty): '2.18 (commit 37996a0a, Thu Jul 21 17:56:14 2016 +0200)' Any idea of what I'm doing wrong? Thanks a lot! Davide