cheat sheets.

==
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[]
[]=
clear    deletes all
default    default value for hash
delete(key)    deletes key from hash
delete(key) {|key|}    deletes key, executes block if key not found
delete_if {|key, value|}    deletes key-value pairs for which block returns true
each
each_key
each_pair
each_value
empty?
fetch(key)     returns value for key, raises IndexError if key not found
fetch(key) {|key|}    returns value for key, executes block if key not found
has_key?
has_value?
include?
index   returns key for given value
indexes
indices
initialize_copy
inspect
invert
key?
keys
length
member?
merge
merge!
new
pretty_print
pretty_print_cycle
rehash   rebuilds hash based on current state
reject   same as delete_if, but works on copy of hash
reject!  same as delete_if, but returns nil if nothing matched
replace(other_hash)  replaces contents of hash with other_hash
select
shift   removes pair from hash and returns it as [key,value]
size
sort
store    alternate element assignment
to_a
to_hash
to_s
to_yaml
update
value?
values
values_at(key, ...) returns an array of values associated with given keys
yaml_initialize