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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_pid(self, unique_id, configs=None):
 """Gets the pid of the process with `unique_id`. If the deployer does not know of a process with `unique_id` then it should return a value of constants.PROCESS_NOT_RUNNING_PID """

    RECV_BLOCK_SIZE = 16
    # the following is necessay to set the configs for this function as the combination of the
    # default configurations and the parameter with the parameter superceding the defaults but
    # not modifying the defaults
    if configs is None:
      configs = {}
    tmp = self.default_configs.copy()
    tmp.update(configs)
    configs = tmp

    if unique_id in self.processes:
      hostname = self.processes[unique_id].hostname
    else:
      return constants.PROCESS_NOT_RUNNING_PID

    if self.processes[unique_id].start_command is None:
      return constants.PROCESS_NOT_RUNNING_PID

    if self.processes[unique_id].pid_file is not None:
      with open_remote_file(hostname, self.processes[unique_id].pid_file,
                            username=runtime.get_username(), password=runtime.get_password()) as pid_file:
        full_output = pid_file.read()
    elif 'pid_file' in configs.keys():
      with open_remote_file(hostname, configs['pid_file'],
                            username=runtime.get_username(), password=runtime.get_password()) as pid_file:
        full_output = pid_file.read()
    else:
      pid_keyword = self.processes[unique_id].start_command
      if self.processes[unique_id].args is not None:
        pid_keyword = "{0} {1}".format(pid_keyword, ' '.join(self.processes[unique_id].args))
      pid_keyword = configs.get('pid_keyword', pid_keyword)
      # TODO(jehrlich): come up with a simpler approach to this
      pid_command = "ps aux | grep '{0}' | grep -v grep | tr -s ' ' | cut -d ' ' -f 2 | grep -Eo '[0-9]+'".format(pid_keyword)
      pid_command = configs.get('pid_command', pid_command)
      non_failing_command = "{0}; if [ $? -le 1 ]; then true;  else false; fi;".format(pid_command)
      env = configs.get("env", {})
      with get_ssh_client(hostname, username=runtime.get_username(), password=runtime.get_password()) as ssh:
        chan = exec_with_env(ssh, non_failing_command, msg="Failed to get PID", env=env)
      output = chan.recv(RECV_BLOCK_SIZE)
      full_output = output
      while len(output) > 0:
        output = chan.recv(RECV_BLOCK_SIZE)
        full_output += output
    if len(full_output) > 0:
      pids = [int(pid_str) for pid_str in full_output.split('\n') if pid_str.isdigit()]
      if len(pids) > 0:
        return pids

    return constants.PROCESS_NOT_RUNNING_PID