Respected Chimera team!

I have a pdb file in which i have done mutation by using swapaa command in IDLE python

but once i saved the structure then new saved structure doesn't have mutated residues in it. 

commands:

1.rc("open filename.pdb")

2.rc("swapaa val #0:2.a")

3.new_file_name="val.pdb"

4.rc("write format pdb #0 C:\\Users\\folder" + new_file_name)