class_docstr: Box collection.
  
  BoxList represents a list of bounding boxes as numpy array, where each
  bounding box is represented as a row of 4 numbers,
  [y_min, x_min, y_max, x_max].  It is assumed that all bounding boxes within a
  given list correspond to a single image.
  
  Optionally, users can add additional related fields (such as
  objectness/classification scores).
docstr: Accesses data associated with the specified field in the box collection.
  
  Args:
    field: a string parameter used to speficy a related field to be accessed.
  
  Returns:
    a numpy 1-d array representing data of an associated field
  
  Raises:
    ValueError: if invalid field
code: def get_field(self, field):
      """Accesses data associated with the specified field in the box collection.
  
      Args:
        field: a string parameter used to speficy a related field to be accessed.
  
      Returns:
        a numpy 1-d array representing data of an associated field
  
      Raises:
        ValueError: if invalid field
      """
      if not self.has_field(field):
          raise ValueError("field {} does not exist".format(field))
      return self.data[field]
  
file_path: SlowFast/ava_evaluation/np_box_list.py
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import numpy
label_desc: Use image node_id 7 for calling the BoxList obj's underlying member method code with example usage: obj.get_field(field) and returns: self