Add a text label to the plot of a DataFrame indicated by the provided axis (ax).

    Reference:
       https://stackoverflow.com/a/40979683/623735

def annotate(row, ax, x='x', y='y', text='name', xytext=(7, -5), textcoords='offset points', **kwargs):
    """Add a text label to the plot of a DataFrame indicated by the provided axis (ax).

    Reference:
       https://stackoverflow.com/a/40979683/623735
    """
    # idx = row.name
    text = row[text] if text in row else str(text)
    x = row[x] if x in row else float(x)
    y = row[y] if y in row else float(y)
    ax.annotate(text, (row[x], row[y]), xytext=xytext, textcoords=textcoords, **kwargs)
    return row[text]