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Given the following text description, write Python code to implement the functionality described below step by step
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Description:
 This notebook can be used to test the basic features of a Catalog object, which is defined in by the class definition in skyofstars/catalogs.py. This will only work if you have installed sky-of-stars as a package, as described in the README.
Step1:  We defined a new kind of Python variable, by writing a class definition for a Catalog. We can create a new one of these objects as follows.
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Python Code:
# import everything from skyofstars
from skyofstars.examples import *
example = create_test_catalog()
Explanation: This notebook can be used to test the basic features of a Catalog object, which is defined in by the class definition in skyofstars/catalogs.py. This will only work if you have installed sky-of-stars as a package, as described in the README.
End of explanation
example.coordinates = example.coordinates.transform_to('icrs')
print (example.coordinates.icrs.ra.rad)
# we can also access all the functions we defined *inside* the Catalog
example.plot_celestial(s=5, alpha=0.2)
# we can list all the stuff defined inside the Catalog like this:
dir(example)
Explanation: We defined a new kind of Python variable, by writing a class definition for a Catalog. We can create a new one of these objects as follows.
End of explanation
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