code: def _get_is_sub_and_is_first_input(pattern):
      is_sub = pattern.add_or_sub.op_type == "sub"
      is_first_input = pattern.add_or_sub.x == pattern.linear.outputs[0]
      return is_sub, is_first_input
  
file_path: coremltools/coremltools/converters/mil/experimental/passes/generic_linear_bias_fusion.py
imports: import os
  import numpy
  from coremltools.converters.mil import Builder
  from coremltools.converters.mil.experimental.passes.generic_pass_infrastructure import register_generic_pass
  from coremltools.converters.mil.mil import get_new_symbol
label_desc: Use image node_id 2 for calling a global function with example usage: _get_is_sub_and_is_first_input(pattern) and returns: is_sub,  is_first_input