Fix YARD docs

lib/mutant/cli.rb

@@ -206,6 +206,8 @@ module Mutant
     #
     # @param [Enumerable<String>] patterns
     #
+    # @return [undefined]
+    #
     # @api private
     #
     def parse_matchers(patterns)
@@ -219,6 +221,8 @@ module Mutant
     #
     # @param [Object]
     #
+    # @return [undefined]
+    #
     # @api private
     #
     def add_strategies(opts)
@@ -235,6 +239,8 @@ module Mutant
     #
     # @param [Object]
     #
+    # @return [undefined]
+    #
     # @api private
     #
     def add_options(opts)

lib/mutant/reporter/cli/printer/subject.rb

@@ -124,6 +124,12 @@ module Mutant
             # Detailed subject printer
             class Details < self
 
+              # Run subject details printer
+              #
+              # @return [undefined]
+              #
+              # @api private
+              #
               def run
                 puts(subject.identification)
                 object.failed_mutations.each do |mutation|