code: def remove_custom_binding(self, key_name, needs_prefix=False):
          
          k = (needs_prefix, key_name)
  
          if k in self.custom_bindings:
              self.custom_key_bindings.remove(self.custom_bindings[k].handler)
              del self.custom_bindings[k]
docs: Remove custom key binding for a key.
  
          :param key_name: Pymux key name, for instance "C-A".