ERROR : <enum_name> is not defined

 #ERROR : Traceback (most recent call last):
#  File "<Script Block >", line 2, in ?
#    rtn = app.ActiveSceneRoot.FindChildren("","",siMeshType)
#NameError: name 'siMeshType' is not defined
# - [line 2]

Possible Cause

This is a message that typically appears when using Python because the constants (enums) are available only as an imported module.

Suggested Solution

You can import the constants module and then specify the name of the constant or enum as its member (see How Do I Get Python to Recognize Softimage Constants (Enums)?).