code: def calculate_dwell_time(
      water_fat_shift, echo_train_length, field_strength
  ):
      """Calculate the dwell time
  
      Parameters
      ----------
      water_fat_shift : float
          The water fat shift of the recording, in pixels.
      echo_train_length : int
          The echo train length of the imaging sequence.
      field_strength : float
          Strength of the magnet in Tesla, e.g. 3.0 for a 3T magnet recording.
  
      Returns
      -------
      dwell_time : float
          The dwell time in seconds.
  
      Raises
      ------
      MRIError
          if values are out of range
      """
      if field_strength < 0:
          raise MRIError("Field strength should be positive")
      if echo_train_length <= 0:
          raise MRIError("Echo train length should be >= 1")
      return (
          (echo_train_length - 1)
          * water_fat_shift
          / (
              GYROMAGNETIC_RATIO
              * PROTON_WATER_FAT_SHIFT
              * field_strength
              * (echo_train_length + 1)
          )
      )
  
label_desc: Use image node_id 1 for calling a global function with example usage: calculate_dwell_time(water_fat_shift, echo_train_length, field_strength) and returns: unknown