code: def is_name_owner( self, name, sender_script_pubkey ):
          
          if not self.is_name_registered( name ):
              # no one owns it 
              return False 
  
          owner = self.get_name_owner( name )
          if owner != sender_script_pubkey:
              return False 
          else:
              return True
docs: Given the fully-qualified name and a sender's script pubkey,
          determine if the sender owns the name.
  
          The name must exist and not be revoked or expired at the
          current block.