Nested code - blocks of code inside blocks of code - is eventually necessary, but increases complexity. This is why keeping the code as flat as
possible, by avoiding unnecessary nesting, is considered a good practice.
Merging if statements when possible will decrease the nesting of the code and improve its readability.
Code like
if condition1:
if condition2: # Noncompliant
# ...
Will be more readable as
if condition1 and condition2: # Compliant
# ...
