File not found error in Jupyter lab using python

I using online jupyterlab which can be accessed through this link below if not then use the second link

This is the second link

So the problem is i have uploaded a .csv format file to the lab but when i try to load it using this code

import pandas as pd
import matplotlib.pyplot as plt
from collections import Counter
import seaborn as sns

df = pd.read_csv ('demo/big.csv')

print(df)

It gives me the following error

FileNotFoundError                         Traceback (most recent call last)
<ipython-input-2-56c1e19c9da6> in <module>
  1 #Task 1
----> 2 df = pd.read_csv ('demo/big.csv')
  3 
  4 print(df)

/srv/conda/envs/notebook/lib/python3.7/site-packages/pandas/io/parsers.py in 
parser_f(filepath_or_buffer, sep, delimiter, header, names, index_col, usecols, squeeze, 
prefix, mangle_dupe_cols, dtype, engine, converters, true_values, false_values, 
skipinitialspace, skiprows, skipfooter, nrows, na_values, keep_default_na, na_filter, 
verbose, 
skip_blank_lines, parse_dates, infer_datetime_format, keep_date_col, date_parser, dayfirst, 
iterator, chunksize, compression, thousands, decimal, lineterminator, quotechar, quoting, 
doublequote, escapechar, comment, encoding, dialect, tupleize_cols, error_bad_lines, 
warn_bad_lines, delim_whitespace, low_memory, memory_map, float_precision)
700                     skip_blank_lines=skip_blank_lines)
701 
--> 702         return _read(filepath_or_buffer, kwds)
703 
704     parser_f.__name__ = name

/srv/conda/envs/notebook/lib/python3.7/site-packages/pandas/io/parsers.py in 
_read(filepath_or_buffer, kwds)
427 
428     # Create the parser.
--> 429     parser = TextFileReader(filepath_or_buffer, **kwds)
430 
431     if chunksize or iterator:

/srv/conda/envs/notebook/lib/python3.7/site-packages/pandas/io/parsers.py in __init__(self, 
f, engine, **kwds)
893             self.options['has_index_names'] = kwds['has_index_names']
894 
--> 895         self._make_engine(self.engine)
896 
897     def close(self):

/srv/conda/envs/notebook/lib/python3.7/site-packages/pandas/io/parsers.py in 
_make_engine(self, engine)
1120     def _make_engine(self, engine='c'):
1121         if engine == 'c':
-> 1122             self._engine = CParserWrapper(self.f, **self.options)
1123         else:
1124             if engine == 'python':

/srv/conda/envs/notebook/lib/python3.7/site-packages/pandas/io/parsers.py in __init__(self, 
src, **kwds)
1851         kwds['usecols'] = self.usecols
1852 
-> 1853         self._reader = parsers.TextReader(src, **kwds)
1854         self.unnamed_cols = self._reader.unnamed_cols
1855 

pandas/_libs/parsers.pyx in pandas._libs.parsers.TextReader.__cinit__()

pandas/_libs/parsers.pyx in pandas._libs.parsers.TextReader._setup_parser_source()

FileNotFoundError: [Errno 2] File b'demo/big.csv' does not exist: b'demo/big.csv'

Please help me out did i gave the path incorrect or what is the problem here?