Returns the complete definition of a custom field's metadata.

        Parameters
        ----------
        custom_field : {Id} Globally unique identifier for the custom field.
        [params] : {Object} Parameters for the request

def find_by_id(self, custom_field, params={}, **options): 
        """Returns the complete definition of a custom field's metadata.

        Parameters
        ----------
        custom_field : {Id} Globally unique identifier for the custom field.
        [params] : {Object} Parameters for the request
        """
        path = "/custom_fields/%s" % (custom_field)
        return self.client.get(path, params, **options)