Added checks to make sure the specified track exists

Added precondition checks to validate input files and paths to return more informative error messages as per #2

node_modules/pretty-format/build/collections.d.ts

@@ -0,0 +1,33 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ */
+import { Config, Printer, Refs } from './types';
+/**
+ * Return entries (for example, of a map)
+ * with spacing, indentation, and comma
+ * without surrounding punctuation (for example, braces)
+ */
+export declare function printIteratorEntries(iterator: any, config: Config, indentation: string, depth: number, refs: Refs, printer: Printer, separator?: string): string;
+/**
+ * Return values (for example, of a set)
+ * with spacing, indentation, and comma
+ * without surrounding punctuation (braces or brackets)
+ */
+export declare function printIteratorValues(iterator: Iterator<any>, config: Config, indentation: string, depth: number, refs: Refs, printer: Printer): string;
+/**
+ * Return items (for example, of an array)
+ * with spacing, indentation, and comma
+ * without surrounding punctuation (for example, brackets)
+ **/
+export declare function printListItems(list: any, config: Config, indentation: string, depth: number, refs: Refs, printer: Printer): string;
+/**
+ * Return properties of an object
+ * with spacing, indentation, and comma
+ * without surrounding punctuation (for example, braces)
+ */
+export declare function printObjectProperties(val: Record<string, any>, config: Config, indentation: string, depth: number, refs: Refs, printer: Printer): string;
+//# sourceMappingURL=collections.d.ts.map