You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: spanner_postgresql_functions.rb
    path of file: ./repos/ruby-docs-samples/spanner
    
    the code of the file until where you have to start completion: # Copyright 2022 Google, Inc
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, softw
    
def spanner_postgresql_functions project_id:, instance_id:, database_id:
  # project_id  = "Your Google Cloud project ID"
  # instance_id = "Your Spanner instance ID"
  # database_id = "Your Spanner database ID"

  spanner = Google::Cloud::Spanner.new project: project_id
  client  = spanner.client instance_id, database_id

  # Use the PostgreSQL `to_timestamp` function to convert a number of seconds since epoch to a
  # timestamp. 1284352323 seconds = Monday, September 13, 2010 4:32:03 AM.
  results = client.execute "SELECT to_timestamp(1284352323) AS t"

  results.rows.each do |row|
    puts "Timestamp #{row[:t]}"
  end
end