Fixed dosctrings in step function #2122

Job	Run time
Build documentation	2m 50s
Build documentation	5m 52s
Test pygama with Python (3.9, ubuntu-latest)	1m 41s
Test pygama with Python (3.9, ubuntu-latest)	5m 36s
Calculate and upload test coverage	1m 54s
Calculate and upload test coverage	5m 55s
Test pygama with Python (3.9, macOS-13)	2m 21s
Test pygama with Python (3.9, macOS-13)	9m 46s
Test pygama with Python (3.10, ubuntu-latest)	1m 48s
Test pygama with Python (3.10, ubuntu-latest)	4m 53s
Test pygama with Python (3.10, macOS-13)	2m 2s
Test pygama with Python (3.10, macOS-13)	7m 34s
Test pygama with Python (3.11, ubuntu-latest)	1m 39s
Test pygama with Python (3.11, ubuntu-latest)	4m 49s
Test pygama with Python (3.11, macOS-13)	2m 3s
Test pygama with Python (3.11, macOS-13)	7m 44s
	1h 8m 27s

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