Build notebooks

The first function we will define for our new Python package is called nbuild().

nbuild() will

Create a new notebook with the new_notebook() function from the v4 module of nbformat
Read the file contents from a list of source files with the read_file() function that we have used in previous exercises
Pass the file contents to the new_code_cell() or new_markdown_cell() functions from the v4 module of nbformat
Assign a list of the resulting cells to the 'cells' key in the new notebook
Return the notebook instance

We've already imported nbformat and all of the above functions.

With nbuild(), we will be able to create Jupyter notebooks from small, modular files!

Create new code cells from the contents of files that end in .py.
Create new markdown cells from the contents of all other files.