Style/RedundantSelf: Redundant `self` detected. (https://rubystyle.guide#no-self-unless-required)

Style/ParenthesesAroundCondition: Don't use parentheses around the condition of an `if`. (https://rubystyle.guide#no-parens-around-condition)

Style/IfUnlessModifier: Favor modifier `if` usage when having a single-line body. Another good alternative is the usage of control flow `&&`/`||`. (https://rubystyle.guide#if-as-a-modifier)

Style/SoleNestedConditional: Consider merging nested conditions into outer `if` conditions.

Style/RedundantSelfAssignment: Redundant self assignment detected. Method `append` modifies its receiver in place.

Style/StringLiterals: Prefer single-quoted strings when you don't need string interpolation or special symbols. (https://rubystyle.guide#consistent-string-literals)