code: function isImported(source, classifiedName, importPath) {
      const allNodes = getSourceNodes(source);
      const matchingNodes = allNodes
          .filter(node => node.kind === ts.SyntaxKind.ImportDeclaration)
          .filter((imp) => imp.moduleSpecifier.kind === ts.SyntaxKind.StringLiteral)
          .filter((imp) => {
          return imp.moduleSpecifier.text === importPath;
      })
          .filter((imp) => {
          if (!imp.importClause) {
              return false;
          }
          const nodes = findNodes(imp.importClause, ts.SyntaxKind.ImportSpecifier).filter(n => n.getText() === classifiedName);
          return nodes.length > 0;
      });
      return matchingNodes.length > 0;
  }
docs: Determine if an import already exists.