title: Pandas - check if dataframe has negative value in any column
body: <p>I wonder how to check if a pandas dataframe has negative value in 1 or more columns and
  return only boolean value (True or False). Can you please help?</p>
  <pre><code>In[1]: df = pd.DataFrame(np.random.randn(10, 3))
  
  In[2]: df
  Out[2]:
            0         1         2
  0 -1.783811  0.736010  0.865427
  1 -1.243160  0.255592  1.670268
  2  0.820835  0.246249  0.288464
  3 -0.923907 -0.199402  0.090250
  4 -1.575614 -1.141441  0.689282
  5 -1.051722  0.513397  1.471071
  6  2.549089  0.977407  0.686614
  7 -1.417064  0.181957  0.351824
  8  0.643760  0.867286  1.166715
  9 -0.316672 -0.647559  1.331545
  
  </code></pre>
  <p>Expected output:-</p>
  <pre><code>Out[3]: True
  </code></pre>