Logstash ruby filter - remove leafs of a path selected by regexp

pipeline.conf

# input sample: {"name": "John", "outer": {"inner": {"leaf_1": "a leaf 1", "leaf_2": "a leaf 2", "leaf_3": "a leaf 3"}}}

input {
	stdin {
		codec => json
	}
}

filter {
  ruby {
    path => "${PWD}/regexp_dropper.rb"
    script_params => {
      source => "[outer][inner]"
      field_regexp => "leaf_[1, 2]"
    }
  }
}

output {
	stdout {
		codec => rubydebug
	}
}

regexp_dropper.rb

#Usage:
# source: is path tot he parent node where to delete the fields, must be in format [field_parent][field_middle]
# field_regexp: is regexp that has to be matched to remove a field, example field_{1, 2} will remove [field_parent][field_middle][field_1] and [field_parent][field_middle][field_2]

def register(params)
  params = params.dup
  @source = params.delete("source")
  @field_regexp = params.delete("field_regexp")
  params.empty? || report_configuration_error("unknown script parameter(s): #{params.keys}.")
end	

def filter(event)
  source_map = @source.nil? ? event.to_hash : event.get(@source)

  return [event] unless source_map

  fail('source not a key/value map') unless source_map.kind_of?(Hash)

  source_map.keys.each do |key|
  	if key =~ Regexp.new(@field_regexp)
  	  # remove if match the leaf name
  	  full_path = "#{@source}[#{key}]"	
  	  #logger.info("field to remove: #{full_path}")
  	  event.remove(full_path)
  	end
  end
  [event]
end


def report_configuration_error(message)
  raise LogStash::ConfigurationError, message
end