input: Write a python function to encode a text into base64.
  assert encode_base64('This is a test') == 'VGhpcyBpcyBhIHRlc3Q='
  assert encode_base64('Hello, World!') == 'SGVsbG8sIFdvcmxkIQ=='
  assert encode_base64('Python is awesome!') == 'UHl0aG9uIGlzIGF3ZXNvbWUh'
output: def encode_base64(text):
      import base64
      encoded_bytes = base64.b64encode(text.encode('utf-8'))
      encoded_str = encoded_bytes.decode('utf-8')
      return encoded_str