      html_cutoff = None
      html_cutoff_text = _('More than {count} items...')
  
      def __init__(self, choices, **kwargs):
          self.grouped_choices = to_choices_dict(choices)
          self.choices = flatten_choices_dict(self.grouped_choices)
          self.html_cutoff = kwargs.pop('html_cutoff', self.html_cutoff)
          self.html_cutoff_text = kwargs.pop('html_cutoff_text', self.html_cutoff_text)
  
          # Map the string representation of choices to the underlying value.
          # Allows us to deal with eg. integer choices while supporting either
 
</s> remove         # Map the string representation of choices to the underlying value.
        # Allows us to deal with eg. integer choices while supporting either
        # integer or string input, but still get the correct datatype out.
        self.choice_strings_to_values = {
            six.text_type(key): key for key in self.choices.keys()
        }

 </s> add 
        self.choices = choices
      html_cutoff = None
      html_cutoff_text = _('More than {count} items...')
  
      def __init__(self, choices, **kwargs):
        self.choices = choices
        self.choices = choices
          self.html_cutoff = kwargs.pop('html_cutoff', self.html_cutoff)
          self.html_cutoff_text = kwargs.pop('html_cutoff_text', self.html_cutoff_text)
  
          # Map the string representation of choices to the underlying value.
          # Allows us to deal with eg. integer choices while supporting either
keep keep keep keep replace replace keep keep keep keep keep
 Allow `ChoiceField.choices` to be set dynamically (#5426)

## Description

The `choices` field for the `ChoiceField` class should be able to be edited after `ChoiceField.__init__` is called.

```
field = ChoiceField(choices=[1,2])
field.choices = [1]  # Should no longer allow `2` as a choice
```

Currently, you must update `choices`, `grouped_choices`, and `choice_strings_to_values` to achieve this. This P/R keeps `grouped_choices` and `choice_strings_to_values` in sync whenever the `choices` are edited. 
rest_framework/fields.py