code: public boolean removeChild( AstNode child ) {
          boolean result = this.children.remove(child);
          if (result) {
              child.parent = null;
          }
          return result;
      }
docs: Remove the node from this node.
  
  @param child the child node; may not be null
  @return true if the child was removed from this node, or false if the supplied node was not a child of this node