class_docstr: FocalLossCost.
  
  Args:
      weight (int | float, optional): loss_weight
      alpha (int | float, optional): focal_loss alpha
      gamma (int | float, optional): focal_loss gamma
      eps (float, optional): default 1e-12
      binary_input (bool, optional): Whether the input is binary,
         default False.
class_docstr_tok: ["FocalLossCost",".","Args",":","weight","(","int","|","float",",","optional",")",":","loss_weight","alpha","(","int","|","float",",","optional",")",":","focal_loss","alpha","gamma","(","int","|","float",",","optional",")",":","focal_loss","gamma","eps","(","float",",","optional",")",":","default","1e-12","binary_input","(","bool",",","optional",")",":","Whether","the","input","is","binary",",","default","False","."]
code: def __init__(
      self,
      weight=1.0,
      alpha=0.25,
      gamma=2,
      eps=1e-12,
      binary_input=False,
  ):
      self.weight = weight
      self.alpha = alpha
      self.gamma = gamma
      self.eps = eps
      self.binary_input = binary_input
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import numpy
  import paddle
  import paddle.nn.functional
  from ppdet.core.workspace import register
label_desc: Use image node_id 1 to create a new FocalLossCost object  with example: obj = FocalLossCost(weight, alpha, gamma, eps, binary_input)