code: def _parse_pem_data(pem_data):
      
      sep = '-----BEGIN CERTIFICATE-----'
      cert_chain = [six.b(sep + s) for s in pem_data.split(sep)[1:]]
      certs = []
      load_cert = x509.load_pem_x509_certificate
      for cert in cert_chain:
          try:
              certs.append(load_cert(cert, default_backend()))
          except ValueError:
              warnings.warn('Certificate is invalid.')
              return False
  
      return certs
docs: Parse PEM-encoded X.509 certificate chain.
  
      Args:
          pem_data: str. PEM file retrieved from SignatureCertChainUrl.
  
      Returns:
          list or bool: If url is valid, returns the certificate chain as a list
              of cryptography.hazmat.backends.openssl.x509._Certificate
              certificates where certs[0] is the first certificate in the file; if
              url is invalid, returns False.