code: function isConstantFunction (node) {
    return isFunctionDefinition(node) && (
      node.attributes.constant === true ||
      node.attributes.stateMutability === 'view' ||
      node.attributes.stateMutability === 'pure'
    )
  }
docs: True if is function defintion that is flaged as constant
  @node {ASTNode} some AstNode
  @return {bool}