docstr: Reads a frame from a list and index for the asked environment ids
  
  :param arr: (np.ndarray) the array that is read
  :param idx: ([int]) the idx that are read
  :param envx: ([int]) the idx for the environments
  :return: ([float]) the askes frames from the list
code: def take(self, arr, idx, envx):
      """
      Reads a frame from a list and index for the asked environment ids
  
      :param arr: (np.ndarray) the array that is read
      :param idx: ([int]) the idx that are read
      :param envx: ([int]) the idx for the environments
      :return: ([float]) the askes frames from the list
      """
      n_env = self.n_env
      out = np.empty([n_env] + list(arr.shape[2:]), dtype=arr.dtype)
      for i in range(n_env):
          out[i] = arr[idx[i], envx[i]]
      return out
  
file_path: stable-baselines/stable_baselines/acer/buffer.py
imports: import numpy
label_desc: Use image node_id 6 for calling the Buffer obj's underlying member method code with example usage: obj.take(arr, idx, envx) and returns: out