keep_if
examples
d = { a: 1, b: 2 } d.keep_if(Integer) d
d = { a: 1, b: 2 } d.keep_if { |key| key == :a } d
d = { a: 1, b: 2 } d.keep_if { |key, value| value.one? } d
d = { a: 1, b: 2 } d.keep_if { |key, value, index| index.zero? } d
d = { a: 1, b: 2 } d.keep_if { |key, value, index, dictionary| dictionary.many? } d