class Jekyll::Plugin

def self.<=>(other)

Returns -1, 0, 1.

other - The class to be compared.

Spaceship is priority [higher -> lower] 
def self.<=>(other)
  PRIORITIES[other.priority] <=> PRIORITIES[self.priority]
end

def self.inherited(base)

Returns nothing.

base - The Class subclass.

ever called by Ruby itself.
Install a hook so that subclasses are recorded. This method is only 
def self.inherited(base)
  subclasses << base
  subclasses.sort!
end

def self.priority(priority = nil)

Returns the Symbol priority.

:lowest, :low, :normal, :high, :highest
priority - The Symbol priority (default: nil). Valid options are:

set the priority.
argument it returns the priority. When an argument is given, it will
Get or set the priority of this plugin. When called without an 
def self.priority(priority = nil)
  @priority ||= nil
  if priority && PRIORITIES.has_key?(priority)
    @priority = priority
  end
  @priority || :normal
end

def self.safe(safe = nil)

Returns the safety Boolean.

safe - The Boolean safety (default: nil).

safety.
it returns the safety. When an argument is given, it will set the
Get or set the safety of this plugin. When called without an argument 
def self.safe(safe = nil)
  if safe
    @safe = safe
  end
  @safe || false
end

def self.subclasses

Returns an Array of Class objects.

The list of Classes that have been subclassed. 
def self.subclasses
  @subclasses ||= []
end

def initialize(config = {})

Returns a new instance.

config - The Hash of configuration options.

Initialize a new plugin. This should be overridden by the subclass. 
def initialize(config = {})
  # no-op for default
end