code: function isExternalDirectCall (node) {
    return isMemberAccess(node, basicRegex.EXTERNALFUNCTIONTYPE, undefined, basicRegex.CONTRACTTYPE, undefined) && !isThisLocalCall(node) && !isSuperLocalCall(node)
  }
docs: True if it is an external call via defined interface (not low level call)
  @node {ASTNode} some AstNode
  @return {bool}