src/reducers/map.js
function removeGroup(state, action) {
  const groups = state.metadata ? Object.assign({}, state.metadata[GROUPS_KEY]) : {};
  delete groups[action.id];
  const metadata = {};
  metadata[GROUPS_KEY] = groups;
  return Object.assign({}, state, {
    metadata: Object.assign({}, state.metadata, metadata),
  });
}
function removeGroup(state, action) {
  const groups = state.metadata ? Object.assign({}, state.metadata[GROUPS_KEY]) : {};
  delete groups[action.id];
  const metadata = {};
  metadata[GROUPS_KEY] = groups;
  return Object.assign({}, state, {
    metadata: Object.assign({}, state.metadata, metadata),
  });
}
Remove a group from the map's metadata section.
@param {Object} state The redux state.
@param {Object} action The action object.

@returns {Object} The new state object.