  def is_simple_callable(obj):
      """
      True if the object is a callable that takes no arguments.
      """
      if not (inspect.isfunction(obj) or inspect.ismethod(obj) or isinstance(obj, functools.partial)):
          return False
  
      sig = inspect.signature(obj)
      params = sig.parameters.values()
 
</s> remove from rest_framework.fields import DjangoImageField, is_simple_callable
 </s> add from rest_framework.fields import (
    BuiltinSignatureError, DjangoImageField, is_simple_callable
)
    # Bail early since we cannot inspect built-in function signatures.
    if inspect.isbuiltin(obj):
        raise BuiltinSignatureError(
            'Built-in function signatures are not inspectable. '
            'Wrap the function call in a simple, pure Python function.')

  def is_simple_callable(obj):
      """
      True if the object is a callable that takes no arguments.
      """
    # Bail early since we cannot inspect built-in function signatures.
    if inspect.isbuiltin(obj):
        raise BuiltinSignatureError(
            'Built-in function signatures are not inspectable. '
            'Wrap the function call in a simple, pure Python function.')

      if not (inspect.isfunction(obj) or inspect.ismethod(obj) or isinstance(obj, functools.partial)):
          return False
  
      sig = inspect.signature(obj)
      params = sig.parameters.values()
keep keep keep add keep keep keep keep keep
 Raise exception when field source is a built-in (#6766) 
rest_framework/fields.py