class PG::Tuple

def each_key(&block) 

def each_key(&block)
	if fn=field_names
		fn.each(&block)
	else
		field_map.each_key(&block)
	end
end

def has_key?(key) 

def has_key?(key)
	field_map.has_key?(key)
end

def inspect

## Return a String representation of the object suitable for debugging. 
def inspect
	"#<#{self.class} #{self.map{|k,v| "#{k}: #{v.inspect}" }.join(", ") }>"
end

def keys 

def keys
	field_names || field_map.keys.freeze
end