. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 3.2 Upgrading To Newer Releases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 In Click 2.0 the signature for callbacks changed. For more information about these changes see Upgrading to 2.0. 1.5.12 Yes Parameters For dangerous operations, it’s very useful to be able to ask a user In Click 2.0 the signature for callbacks changed. For more information about these changes see Upgrading to 2.0. 1.5.13 Values from Environment Variables A very useful feature of Click is the ability