Implement main set of filters

[flexferrum]

The following filters should be implemented:

• join
• sort
• default
• first
• last
• length
• max
• min
• reverse
• unique
• sum
• attr
• map
• reject
• rejectattr
• select
• selectattr
• pprint
• dictsort
• abs
• float
• int
• list
• round
• random
• trim
• title
• upper
• wordcount
• replace
• truncate
• groupby

[flexferrum]

#11

[flexferrum]

#12

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#13

[flexferrum]

#15

[flexferrum]

#17

[flexferrum]

#18

[flexferrum]

#19

[flexferrum]

#20