class_docstr: Reads a fixed-width file using a column schema in CSV format.
  
  This works almost exactly like Python's built-in CSV reader.
  
  Schemas must be in the "ffs" format, with :code:`column`, :code:`start`,
  and :code:`length` columns. There is a repository of such schemas
  maintained at `wireservice/ffs <https://github.com/wireservice/ffs>`_.
code: def __init__(self, f, schema_f):
      from agate import csv
  
      self.file = f
      self.fields = []
  
      reader = csv.reader(schema_f)
      header = next(reader)
  
      if header != ["column", "start", "length"]:
          raise ValueError(
              'Schema must contain exactly three columns: "column", "start", and "length".'
          )
  
      for row in reader:
          self.fields.append(Field(row[0], int(row[1]), int(row[2])))
  
file_path: agate/agate/fixed.py
imports: from collections import OrderedDict, namedtuple
label_desc: Use image node_id 1 to create a new Reader object  with example: obj = Reader(f, schema_f)