How do you use inverseTimes()?

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How do you use inverseTimes?

From reading the docs, it looks like it should be a member function of Transform(), and take another Transform() as the argument.

However, the following code:

from geometry_msgs.msg import Transform
my_tf1 = Transform()
my_tf2 = Transform()
my_tf1.translation.x = 2
my_tf2.translation.x = 5
my_tf1.inverseTimes(my_tf2)

produces the error:

AttributeError: 'Transform' object has no attribute 'inverseTimes'

Is there a different object in tf called Transform that I should be using instead?